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In This Article Expand or collapse the "in this article" section Qualitative Comparative Analysis (QCA)

Introduction.

• The Emergence of QCA
• Comparisons with Other Techniques
• Criticisms of QCA
• Case Selection and Combining Cross-Case and Within-Case Analysis
• Model Specification and Parameters of Fit
• Applications of QCA
• QCA Software

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• Qualitative Methods in Sociological Research
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Qualitative Comparative Analysis (QCA) by Axel Marx LAST REVIEWED: 28 November 2016 LAST MODIFIED: 28 November 2016 DOI: 10.1093/obo/9780199756384-0188

The social sciences use a wide range of research methods and techniques ranging from experiments to techniques which analyze observational data such as statistical techniques, qualitative text analytic techniques, ethnographies, and many others. In the 1980s a new technique emerged, named Qualitative Comparative Analysis (QCA), which aimed to provide a formalized way to systematically compare a small number (5<N<75) of case studies. John Gerring in the 2001 version of his introduction to social sciences identified QCA as one of the only genuine methodological innovations of the last few decades. In recent years, QCA has also been applied to large-N studies ( Glaesser 2015 , cited under Applications of QCA ; Ragin 2008 , cited under The Essential Features of QCA ) and the application of QCA to perform large-N analysis is in full development. This annotated bibliography aims to provide an overview of the main contributions of QCA as a research technique as well as an introduction to some specific issues as well as QCA applications. The contribution starts with sketching the emergence of QCA and situating the method in the debate between “qualitative” and “quantitative” methods. This contextualization is important to understand and appreciate that QCA in essence is a qualitative case-based research technique and not a quantitative variable-oriented technique. Next, the article discusses some key features of QCA and identifies some of the main books and handbooks on QCA as well as some of the criticism. In a third section, the overview focuses attention on the importance of cases and case selection in QCA. The fourth section introduces the way in which QCA builds explanatory models and presents the key contributions on the selection of explanatory factors, model specification, and testing. The fifth section canvasses the applications of QCA in the social sciences and identifies some interesting examples. Finally, since QCA is a formalized data-analytic technique based on algorithms, the overview ends with an overview of the main software package which can assist in the application of QCA.

Qualitative Case-Based Research in the Social Sciences

This section grounds Qualitative Comparative Analysis (QCA) in the tradition of qualitative case-based methods. As a research approach QCA mainly focuses on the systematic comparison of cases in order to find patterns of difference and similarity between cases. The initial intention of Ragin 1987 (cited under The Essential Features of QCA ) was to develop an original “synthetic strategy” as a middle way between the case-oriented (or “qualitative”) and the variable-oriented (or “quantitative”) approaches, which would “integrate the best features of the case-oriented approach with the best features of the variable-oriented approach” ( Ragin 1987 , p. 84). However, instead of grounding qualitative research on the premises of quantitative research such as King, et al. 1994 did, Ragin aimed to develop a method which is firmly rooted on a case-based qualitative approach ( Ragin and Becker 1992 ; Ragin 1997 for a systematic discussion of the differences between QCA and the approach advocated by King, et al. 1994 ). In recent years the fundamental differences between case-based and variable-oriented approaches have been further elaborated in terms of selection of units of observation or cases, approaches to explanation, causal analysis, measurement of concepts, and external validity (scope and generalization). Many researchers including Charles Ragin, Andrew Bennett ( George and Bennett 2005 ), John Gerring ( Gerring 2007 , Gerring 2012 ), David Collier ( Brady and Collier 2004 ) and James Mahoney ( Mahoney and Rueschemeyer 2003 ) have contributed significantly to identifying the key ontological, epistemological, and logical differences between the two approaches. Goertz and Mahoney 2012 brings this literature together and shows the distinct differences between quantitative and qualitative research. The authors refer to two “cultures” of conducting social-scientific research. In this distinction QCA falls firmly in the “camp” of qualitative research. The overview below identifies some key texts which discuss these differences more in depth.

Brady, H., and D. Collier, eds. 2004. Rethinking social inquiry: Diverse tools, shared standards . Lanham, MD: Rowman and Littlefield.

This edited volume goes into a detailed discussion with King, et al. 1994 and shows the distinctive strengths of different approaches with a strong emphasis on the distinctive strengths of qualitative case-based methods. Book also introduces the idea of process-tracing for within-case analysis. Reprint 2010.

George, A., and A. Bennett. 2005. Case research and theory development . Cambridge, MA: MIT.

Very extensive treatment of how case-based research focusing on longitudinal analysis and process-tracing can contribute to both theory development and theory testing. Discusses many examples from empirical political science research.

Gerring, J. 2007. Case study research: Principles and practice . Cambridge, UK: Cambridge Univ. Press.

Very good introduction into what a case study is and what analytic and descriptive purposes it serves in social science research.

Gerring, J. 2012. Social science methodology: A unified framework . Cambridge, UK: Cambridge Univ. Press.

An update of the 2001 volume which provides a concise introduction to different research approaches and techniques in the social sciences. Clearly shows the added value of different approaches and aims to overcome “the one versus the other” approaches.

Goertz, G., and J. Mahoney. 2012. A tale of two cultures: Qualitative and quantitative research in the social sciences . Princeton, NJ: Princeton Univ. Press.

Book elaborates the differences between qualitative and quantitative research. They elaborate these differences in terms of (1) approaches to explanation, (2) conceptions of causation, (3) approaches toward multivariate explanations, (4) equifinality, (5) scope and causal generalization, (6) case selection, (7) weighting observations, (8) substantively important cases, (9) lack of fit, and (10) concepts and measurement.

King, G., R. Keohane, and S. Verba. 1994. Designing social enquiry: Scientific inference in qualitative research . Princeton, NJ: Princeton Univ. Press.

A much-quoted and highly influential book on research design for the social sciences. This book aimed to discuss and assess qualitative research and argued that qualitative research should be benchmarked against standards used in quantitative research such as never select cases on the dependent variables, making sure one has always more observations than variables, maximize variation, and so on.

Mahoney, J., and D. Rueschemeyer, eds. 2003. Comparative historical analysis in the social sciences . Cambridge, UK: Cambridge Univ. Press.

This is a very impressive volume with chapters written by the best researchers in macro-sociological research and comparative politics. It shows the key strengths of comparative historical research for explaining key social phenomena such as revolutions, social provisions, and democracy. In addition it combines masterfully substantive discussions with methodological implications and challenges and in this way shows how case-based research contributes fundamentally to understanding social change.

Poteete, A., M. Janssen, and E. Ostrom. 2010. Working together: Collective action, the commons and multiple methods in practice . Princeton, NJ: Princeton Univ. Press.

The study of Common Pool Resources (CPRs) has been one of the most theoretically advanced subjects in social sciences. This excellent book introduces different research designs to analyze questions related to the governance of CPRs and situates QCA nicely in the universe of different research designs and strategies.

Ragin, C. C. 1997. Turning the tables: How case-oriented methods challenge variable-oriented methods. Comparative Social Research 16:27–42.

Engages directly with the work of King, et al. 1994 and fundamentally disagrees with its authors Ragin argues that qualitative case-based research is based on different standards and that this type of research should be assessed on the basis of these standards.

Ragin, C. C., and H. Becker. 1992. What is a case? Exploring the foundations of social inquiry . Cambridge, UK: Cambridge Univ. Press.

Brings together leading researchers to discuss the deceptively easy question “what is a case?” and shows the many different approaches toward case-study research. One red line going through the contributions is the emphasis on thinking hard about the question “what is my case a case of?” in theoretical terms.

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• Published: 07 May 2021

The use of Qualitative Comparative Analysis (QCA) to address causality in complex systems: a systematic review of research on public health interventions

• Benjamin Hanckel 1 ,
• Mark Petticrew 2 ,
• James Thomas 3 &
• Judith Green 4  

BMC Public Health volume  21 , Article number:  877 ( 2021 ) Cite this article

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Qualitative Comparative Analysis (QCA) is a method for identifying the configurations of conditions that lead to specific outcomes. Given its potential for providing evidence of causality in complex systems, QCA is increasingly used in evaluative research to examine the uptake or impacts of public health interventions. We map this emerging field, assessing the strengths and weaknesses of QCA approaches identified in published studies, and identify implications for future research and reporting.

PubMed, Scopus and Web of Science were systematically searched for peer-reviewed studies published in English up to December 2019 that had used QCA methods to identify the conditions associated with the uptake and/or effectiveness of interventions for public health. Data relating to the interventions studied (settings/level of intervention/populations), methods (type of QCA, case level, source of data, other methods used) and reported strengths and weaknesses of QCA were extracted and synthesised narratively.

The search identified 1384 papers, of which 27 (describing 26 studies) met the inclusion criteria. Interventions evaluated ranged across: nutrition/obesity ( n  = 8); physical activity ( n  = 4); health inequalities ( n  = 3); mental health ( n  = 2); community engagement ( n  = 3); chronic condition management ( n  = 3); vaccine adoption or implementation ( n  = 2); programme implementation ( n  = 3); breastfeeding ( n  = 2), and general population health ( n  = 1). The majority of studies ( n  = 24) were of interventions solely or predominantly in high income countries. Key strengths reported were that QCA provides a method for addressing causal complexity; and that it provides a systematic approach for understanding the mechanisms at work in implementation across contexts. Weaknesses reported related to data availability limitations, especially on ineffective interventions. The majority of papers demonstrated good knowledge of cases, and justification of case selection, but other criteria of methodological quality were less comprehensively met.

QCA is a promising approach for addressing the role of context in complex interventions, and for identifying causal configurations of conditions that predict implementation and/or outcomes when there is sufficiently detailed understanding of a series of comparable cases. As the use of QCA in evaluative health research increases, there may be a need to develop advice for public health researchers and journals on minimum criteria for quality and reporting.

Peer Review reports

Interest in the use of Qualitative Comparative Analysis (QCA) arises in part from growing recognition of the need to broaden methodological capacity to address causality in complex systems [ 1 , 2 , 3 ]. Guidance for researchers for evaluating complex interventions suggests process evaluations [ 4 , 5 ] can provide evidence on the mechanisms of change, and the ways in which context affects outcomes. However, this does not address the more fundamental problems with trial and quasi-experimental designs arising from system complexity [ 6 ]. As Byrne notes, the key characteristic of complex systems is ‘emergence’ [ 7 ]: that is, effects may accrue from combinations of components, in contingent ways, which cannot be reduced to any one level. Asking about ‘what works’ in complex systems is not to ask a simple question about whether an intervention has particular effects, but rather to ask: “how the intervention works in relation to all existing components of the system and to other systems and their sub-systems that intersect with the system of interest” [ 7 ]. Public health interventions are typically attempts to effect change in systems that are themselves dynamic; approaches to evaluation are needed that can deal with emergence [ 8 ]. In short, understanding the uptake and impact of interventions requires methods that can account for the complex interplay of intervention conditions and system contexts.

To build a useful evidence base for public health, evaluations thus need to assess not just whether a particular intervention (or component) causes specific change in one variable, in controlled circumstances, but whether those interventions shift systems, and how specific conditions of interventions and setting contexts interact to lead to anticipated outcomes. There have been a number of calls for the development of methods in intervention research to address these issues of complex causation [ 9 , 10 , 11 ], including calls for the greater use of case studies to provide evidence on the important elements of context [ 12 , 13 ]. One approach for addressing causality in complex systems is Qualitative Comparative Analysis (QCA): a systematic way of comparing the outcomes of different combinations of system components and elements of context (‘conditions’) across a series of cases.

The potential of qualitative comparative analysis

QCA is an approach developed by Charles Ragin [ 14 , 15 ], originating in comparative politics and macrosociology to address questions of comparative historical development. Using set theory, QCA methods explore the relationships between ‘conditions’ and ‘outcomes’ by identifying configurations of necessary and sufficient conditions for an outcome. The underlying logic is different from probabilistic reasoning, as the causal relationships identified are not inferred from the (statistical) likelihood of them being found by chance, but rather from comparing sets of conditions and their relationship to outcomes. It is thus more akin to the generative conceptualisations of causality in realist evaluation approaches [ 16 ]. QCA is a non-additive and non-linear method that emphasises diversity, acknowledging that different paths can lead to the same outcome. For evaluative research in complex systems [ 17 ], QCA therefore offers a number of benefits, including: that QCA can identify more than one causal pathway to an outcome (equifinality); that it accounts for conjectural causation (where the presence or absence of conditions in relation to other conditions might be key); and that it is asymmetric with respect to the success or failure of outcomes. That is, that specific factors explain success does not imply that their absence leads to failure (causal asymmetry).

QCA was designed, and is typically used, to compare data from a medium N (10–50) series of cases that include those with and those without the (dichotomised) outcome. Conditions can be dichotomised in ‘crisp sets’ (csQCA) or represented in ‘fuzzy sets’ (fsQCA), where set membership is calibrated (either continuously or with cut offs) between two extremes representing fully in (1) or fully out (0) of the set. A third version, multi-value QCA (mvQCA), infrequently used, represents conditions as ‘multi-value sets’, with multinomial membership [ 18 ]. In calibrating set membership, the researcher specifies the critical qualitative anchors that capture differences in kind (full membership and full non-membership), as well as differences in degree in fuzzy sets (partial membership) [ 15 , 19 ]. Data on outcomes and conditions can come from primary or secondary qualitative and/or quantitative sources. Once data are assembled and coded, truth tables are constructed which “list the logically possible combinations of causal conditions” [ 15 ], collating the number of cases where those configurations occur to see if they share the same outcome. Analysis of these truth tables assesses first whether any conditions are individually necessary or sufficient to predict the outcome, and then whether any configurations of conditions are necessary or sufficient. Necessary conditions are assessed by examining causal conditions shared by cases with the same outcome, whilst identifying sufficient conditions (or combinations of conditions) requires examining cases with the same causal conditions to identify if they have the same outcome [ 15 ]. However, as Legewie argues, the presence of a condition, or a combination of conditions in actual datasets, are likely to be “‘quasi-necessary’ or ‘quasi-sufficient’ in that the causal relation holds in a great majority of cases, but some cases deviate from this pattern” [ 20 ]. Following reduction of the complexity of the model, the final model is tested for coverage (the degree to which a configuration accounts for instances of an outcome in the empirical cases; the proportion of cases belonging to a particular configuration) and consistency (the degree to which the cases sharing a combination of conditions align with a proposed subset relation). The result is an analysis of complex causation, “defined as a situation in which an outcome may follow from several different combinations of causal conditions” [ 15 ] illuminating the ‘causal recipes’, the causally relevant conditions or configuration of conditions that produce the outcome of interest.

QCA, then, has promise for addressing questions of complex causation, and recent calls for the greater use of QCA methods have come from a range of fields related to public health, including health research [ 17 ], studies of social interventions [ 7 ], and policy evaluation [ 21 , 22 ]. In making arguments for the use of QCA across these fields, researchers have also indicated some of the considerations that must be taken into account to ensure robust and credible analyses. There is a need, for instance, to ensure that ‘contradictions’, where cases with the same configurations show different outcomes, are resolved and reported [ 15 , 23 , 24 ]. Additionally, researchers must consider the ratio of cases to conditions, and limit the number of conditions to cases to ensure the validity of models [ 25 ]. Marx and Dusa, examining crisp set QCA, have provided some guidance to the ‘ceiling’ number of conditions which can be included relative to the number of cases to increase the probability of models being valid (that is, with a low probability of being generated through random data) [ 26 ].

There is now a growing body of published research in public health and related fields drawing on QCA methods. This is therefore a timely point to map the field and assess the potential of QCA as a method for contributing to the evidence base for what works in improving public health. To inform future methodological development of robust methods for addressing complexity in the evaluation of public health interventions, we undertook a systematic review to map existing evidence, identify gaps in, and strengths and weakness of, the QCA literature to date, and identify the implications of these for conducting and reporting future QCA studies for public health evaluation. We aimed to address the following specific questions [ 27 ]:

1. How is QCA used for public health evaluation? What populations, settings, methods used in source case studies, unit/s and level of analysis (‘cases’), and ‘conditions’ have been included in QCA studies?

2. What strengths and weaknesses have been identified by researchers who have used QCA to understand complex causation in public health evaluation research?

3. What are the existing gaps in, and strengths and weakness of, the QCA literature in public health evaluation, and what implications do these have for future research and reporting of QCA studies for public health?

This systematic review was registered with the International Prospective Register of Systematic Reviews (PROSPERO) on 29 April 2019 ( CRD42019131910 ). A protocol was prepared in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis Protocols (PRISMA-P) 2015 statement [ 28 ], and published in 2019 [ 27 ], where the methods are explained in detail. EPPI-Reviewer 4 was used to manage the process and undertake screening of abstracts [ 29 ].

Search strategy

We searched for peer-reviewed published papers in English, which used QCA methods to examine causal complexity in evaluating the implementation, uptake and/or effects of a public health intervention, in any region of the world, for any population. ‘Public health interventions’ were defined as those which aim to promote or protect health, or prevent ill health, in the population. No date exclusions were made, and papers published up to December 2019 were included.

Search strategies used the following phrases “Qualitative Comparative Analysis” and “QCA”, which were combined with the keywords “health”, “public health”, “intervention”, and “wellbeing”. See Additional file  1 for an example. Searches were undertaken on the following databases: PubMed, Web of Science, and Scopus. Additional searches were undertaken on Microsoft Academic and Google Scholar in December 2019, where the first pages of results were checked for studies that may have been missed in the initial search. No additional studies were identified. The list of included studies was sent to experts in QCA methods in health and related fields, including authors of included studies and/or those who had published on QCA methodology. This generated no additional studies within scope, but a suggestion to check the COMPASSS (Comparative Methods for Systematic Cross-Case Analysis) database; this was searched, identifying one further study that met the inclusion criteria [ 30 ]. COMPASSS ( https://compasss.org/ ) collates publications of studies using comparative case analysis.

We excluded studies where no intervention was evaluated, which included studies that used QCA to examine public health infrastructure (i.e. staff training) without a specific health outcome, and papers that report on prevalence of health issues (i.e. prevalence of child mortality). We also excluded studies of health systems or services interventions where there was no public health outcome.

After retrieval, and removal of duplicates, titles and abstracts were screened by one of two authors (BH or JG). Double screening of all records was assisted by EPPI Reviewer 4’s machine learning function. Of the 1384 papers identified after duplicates were removed, we excluded 820 after review of titles and abstracts (Fig.  1 ). The excluded studies included: a large number of papers relating to ‘quantitative coronary angioplasty’ and some which referred to the Queensland Criminal Code (both of which are also abbreviated to ‘QCA’); papers that reported methodological issues but not empirical studies; protocols; and papers that used the phrase ‘qualitative comparative analysis’ to refer to qualitative studies that compared different sub-populations or cases within the study, but did not include formal QCA methods.

Flow Diagram

Full texts of the 51 remaining studies were screened by BH and JG for inclusion, with 10 papers double coded by both authors, with complete agreement. Uncertain inclusions were checked by the third author (MP). Of the full texts, 24 were excluded because: they did not report a public health intervention ( n  = 18); had used a methodology inspired by QCA, but had not undertaken a QCA ( n  = 2); were protocols or methodological papers only ( n  = 2); or were not published in peer-reviewed journals ( n  = 2) (see Fig.  1 ).

Data were extracted manually from the 27 remaining full texts by BH and JG. Two papers relating to the same research question and dataset were combined, such that analysis was by study ( n  = 26) not by paper. We retrieved data relating to: publication (journal, first author country affiliation, funding reported); the study setting (country/region setting, population targeted by the intervention(s)); intervention(s) studied; methods (aims, rationale for using QCA, crisp or fuzzy set QCA, other analysis methods used); data sources drawn on for cases (source [primary data, secondary data, published analyses], qualitative/quantitative data, level of analysis, number of cases, final causal conditions included in the analysis); outcome explained; and claims made about strengths and weaknesses of using QCA (see Table  1 ). Data were synthesised narratively, using thematic synthesis methods [ 31 , 32 ], with interventions categorised by public health domain and level of intervention.

Quality assessment

There are no reporting guidelines for QCA studies in public health, but there are a number of discussions of best practice in the methodological literature [ 25 , 26 , 33 , 34 ]. These discussions suggest several criteria for strengthening QCA methods that we used as indicators of methodological and/or reporting quality: evidence of familiarity of cases; justification for selection of cases; discussion and justification of set membership score calibration; reporting of truth tables; reporting and justification of solution formula; and reporting of consistency and coverage measures. For studies using csQCA, and claiming an explanatory analysis, we additionally identified whether the number of cases was sufficient for the number of conditions included in the model, using a pragmatic cut-off in line with Marx & Dusa’s guideline thresholds, which indicate how many cases are sufficient for given numbers of conditions to reject a 10% probability that models could be generated with random data [ 26 ].

Overview of scope of QCA research in public health

Twenty-seven papers reporting 26 studies were included in the review (Table  1 ). The earliest was published in 2005, and 17 were published after 2015. The majority ( n  = 19) were published in public health/health promotion journals, with the remainder published in other health science ( n  = 3) or in social science/management journals ( n  = 4). The public health domain(s) addressed by each study were broadly coded by the main area of focus. They included nutrition/obesity ( n  = 8); physical activity (PA) (n = 4); health inequalities ( n  = 3); mental health ( n  = 2); community engagement ( n  = 3); chronic condition management ( n  = 3); vaccine adoption or implementation (n = 2); programme implementation ( n  = 3); breastfeeding ( n  = 2); or general population health ( n  = 1). The majority ( n  = 24) of studies were conducted solely or predominantly in high-income countries (systematic reviews in general searched global sources, but commented that the overwhelming majority of studies were from high-income countries). Country settings included: any ( n  = 6); OECD countries ( n  = 3); USA ( n  = 6); UK ( n  = 6) and one each from Nepal, Austria, Belgium, Netherlands and Africa. These largely reflected the first author’s country affiliations in the UK ( n  = 13); USA ( n  = 9); and one each from South Africa, Austria, Belgium, and the Netherlands. All three studies primarily addressing health inequalities [ 35 , 36 , 37 ] were from the UK.

Eight of the interventions evaluated were individual-level behaviour change interventions (e.g. weight management interventions, case management, self-management for chronic conditions); eight evaluated policy/funding interventions; five explored settings-based health promotion/behaviour change interventions (e.g. schools-based physical activity intervention, store-based food choice interventions); three evaluated community empowerment/engagement interventions, and two studies evaluated networks and their impact on health outcomes.

Methods and data sets used

Fifteen studies used crisp sets (csQCA), 11 used fuzzy sets (fsQCA). No study used mvQCA. Eleven studies included additional analyses of the datasets drawn on for the QCA, including six that used qualitative approaches (narrative synthesis, case comparisons), typically to identify cases or conditions for populating the QCA; and four reporting additional statistical analyses (meta-regression, linear regression) to either identify differences overall between cases prior to conducting a QCA (e.g. [ 38 ]) or to explore correlations in more detail (e.g. [ 39 ]). One study used an additional Boolean configurational technique to reduce the number of conditions in the QCA analysis [ 40 ]. No studies reported aiming to compare the findings from the QCA with those from other techniques for evaluating the uptake or effectiveness of interventions, although some [ 41 , 42 ] were explicitly using the study to showcase the possibilities of QCA compared with other approaches in general. Twelve studies drew on primary data collected specifically for the study, with five of those additionally drawing on secondary data sets; five drew only on secondary data sets, and nine used data from systematic reviews of published research. Seven studies drew primarily on qualitative data, generally derived from interviews or observations.

Many studies were undertaken in the context of one or more trials, which provided evidence of effect. Within single trials, this was generally for a process evaluation, with cases being trial sites. Fernald et al’s study, for instance, was in the context of a trial of a programme to support primary care teams in identifying and implementing self-management support tools for their patients, which measured patient and health care provider level outcomes [ 43 ]. The QCA reported here used qualitative data from the trial to identify a set of necessary conditions for health care provider practices to implement the tools successfully. In studies drawing on data from systematic reviews, cases were always at the level of intervention or intervention component, with data included from multiple trials. Harris et al., for instance, undertook a mixed-methods systematic review of school-based self-management interventions for asthma, using meta-analysis methods to identify effective interventions and QCA methods to identify which intervention features were aligned with success [ 44 ].

The largest number of studies ( n  = 10), including all the systematic reviews, analysed cases at the level of the intervention, or a component of the intervention; seven analysed organisational level cases (e.g. school class, network, primary care practice); five analysed sub-national region level cases (e.g. state, local authority area), and two each analysed country or individual level cases. Sample sizes ranged from 10 to 131, with no study having small N (< 10) sample sizes, four having large N (> 50) sample sizes, and the majority (22) being medium N studies (in the range 10–50).

Rationale for using QCA

Most papers reported a rationale for using QCA that mentioned ‘complexity’ or ‘context’, including: noting that QCA is appropriate for addressing causal complexity or multiple pathways to outcome [ 37 , 43 , 45 , 46 , 47 , 48 , 49 , 50 , 51 ]; noting the appropriateness of the method for providing evidence on how context impacts on interventions [ 41 , 50 ]; or the need for a method that addressed causal asymmetry [ 52 ]. Three stated that the QCA was an ‘exploratory’ analysis [ 53 , 54 , 55 ]. In addition to the empirical aims, several papers (e.g. [ 42 , 48 ]) sought to demonstrate the utility of QCA, or to develop QCA methods for health research (e.g. [ 47 ]).

Reported strengths and weaknesses of approach

There was a general agreement about the strengths of QCA. Specifically, that it was a useful tool to address complex causality, providing a systematic approach to understand the mechanisms at work in implementation across contexts [ 38 , 39 , 43 , 45 , 46 , 47 , 55 , 56 , 57 ], particularly as they relate to (in) effective intervention implementation [ 44 , 51 ] and the evaluation of interventions [ 58 ], or “where it is not possible to identify linearity between variables of interest and outcomes” [ 49 ]. Authors highlighted the strengths of QCA as providing possibilities for examining complex policy problems [ 37 , 59 ]; for testing existing as well as new theory [ 52 ]; and for identifying aspects of interventions which had not been previously perceived as critical [ 41 ] or which may have been missed when drawing on statistical methods that use, for instance, linear additive models [ 42 ]. The strengths of QCA in terms of providing useful evidence for policy were flagged in a number of studies, particularly where the causal recipes suggested that conventional assumptions about effectiveness were not confirmed. Blackman et al., for instance, in a series of studies exploring why unequal health outcomes had narrowed in some areas of the UK and not others, identified poorer outcomes in settings with ‘better’ contracting [ 35 , 36 , 37 ]; Harting found, contrary to theoretical assumptions about the necessary conditions for successful implementation of public health interventions, that a multisectoral network was not a necessary condition [ 30 ].

Weaknesses reported included the limitations of QCA in general for addressing complexity, as well as specific limitations with either the csQCA or the fsQCA methods employed. One general concern discussed across a number of studies was the problem of limited empirical diversity, which resulted in: limitations in the possible number of conditions included in each study, particularly with small N studies [ 58 ]; missing data on important conditions [ 43 ]; or limited reported diversity (where, for instance, data were drawn from systematic reviews, reflecting publication biases which limit reporting of ineffective interventions) [ 41 ]. Reported methodological limitations in small and intermediate N studies included concerns about the potential that case selection could bias findings [ 37 ].

In terms of potential for addressing causal complexity, the limitations of QCA for identifying unintended consequences, tipping points, and/or feedback loops in complex adaptive systems were noted [ 60 ], as were the potential limitations (especially in csQCA studies) of reducing complex conditions, drawn from detailed qualitative understanding, to binary conditions [ 35 ]. The impossibility of doing this was a rationale for using fsQCA in one study [ 57 ], where detailed knowledge of conditions is needed to make theoretically justified calibration decisions. However, others [ 47 ] make the case that csQCA provides more appropriate findings for policy: dichotomisation forces a focus on meaningful distinctions, including those related to decisions that practitioners/policy makers can action. There is, then, a potential trade-off in providing ‘interpretable results’, but ones which preclude potential for utilising more detailed information [ 45 ]. That QCA does not deal with probabilistic causation was noted [ 47 ].

Quality of published studies

Assessment of ‘familiarity with cases’ was made subjectively on the basis of study authors’ reports of their knowledge of the settings (empirical or theoretical) and the descriptions they provided in the published paper: overall, 14 were judged as sufficient, and 12 less than sufficient. Studies which included primary data were more likely to be judged as demonstrating familiarity ( n  = 10) than those drawing on secondary sources or systematic reviews, of which only two were judged as demonstrating familiarity. All studies justified how the selection of cases had been made; for those not using the full available population of cases, this was in general (appropriately) done theoretically: following previous research [ 52 ]; purposively to include a range of positive and negative outcomes [ 41 ]; or to include a diversity of cases [ 58 ]. In identifying conditions leading to effective/not effective interventions, one purposive strategy was to include a specified percentage or number of the most effective and least effective interventions (e.g. [ 36 , 40 , 51 , 52 ]). Discussion of calibration of set membership scores was judged adequate in 15 cases, and inadequate in 11; 10 reported raw data matrices in the paper or supplementary material; 21 reported truth tables in the paper or supplementary material. The majority ( n  = 21) reported at least some detail on the coverage (the number of cases with a particular configuration) and consistency (the percentage of similar causal configurations which result in the same outcome). The majority ( n  = 21) included truth tables (or explicitly provided details of how to obtain them); fewer ( n  = 10) included raw data. Only five studies met all six of these quality criteria (evidence of familiarity with cases, justification of case selection, discussion of calibration, reporting truth tables, reporting raw data matrices, reporting coverage and consistency); a further six met at least five of them.

Of the csQCA studies which were not reporting an exploratory analysis, four appeared to have insufficient cases for the large number of conditions entered into at least one of the models reported, with a consequent risk to the validity of the QCA models [ 26 ].

QCA has been widely used in public health research over the last decade to advance understanding of causal inference in complex systems. In this review of published evidence to date, we have identified studies using QCA to examine the configurations of conditions that lead to particular outcomes across contexts. As noted by most study authors, QCA methods have promised advantages over probabilistic statistical techniques for examining causation where systems and/or interventions are complex, providing public health researchers with a method to test the multiple pathways (configurations of conditions), and necessary and sufficient conditions that lead to desired health outcomes.

The origins of QCA approaches are in comparative policy studies. Rihoux et al’s review of peer-reviewed journal articles using QCA methods published up to 2011 found the majority of published examples were from political science and sociology, with fewer than 5% of the 313 studies they identified coming from health sciences [ 61 ]. They also reported few examples of the method being used in policy evaluation and implementation studies [ 62 ]. In the decade since their review of the field [ 61 ], there has been an emerging body of evaluative work in health: we identified 26 studies in the field of public health alone, with the majority published in public health journals. Across these studies, QCA has been used for evaluative questions in a range of settings and public health domains to identify the conditions under which interventions are implemented and/or have evidence of effect for improving population health. All studies included a series of cases that included some with and some without the outcome of interest (such as behaviour change, successful programme implementation, or good vaccination uptake). The dominance of high-income countries in both intervention settings and author affiliations is disappointing, but reflects the disproportionate location of public health research in the global north more generally [ 63 ].

The largest single group of studies included were systematic reviews, using QCA to compare interventions (or intervention components) to identify successful (and non-successful) configurations of conditions across contexts. Here, the value of QCA lies in its potential for synthesis with quantitative meta-synthesis methods to identify the particular conditions or contexts in which interventions or components are effective. As Parrott et al. note, for instance, their meta-analysis could identify probabilistic effects of weight management programmes, and the QCA analysis enabled them to address the “role that the context of the [paediatric weight management] intervention has in influencing how, when, and for whom an intervention mix will be successful” [ 50 ]. However, using QCA to identify configurations of conditions that lead to effective or non- effective interventions across particular areas of population health is an application that does move away in some significant respects from the origins of the method. First, researchers drawing on evidence from systematic reviews for their data are reliant largely on published evidence for information on conditions (such as the organisational contexts in which interventions were implemented, or the types of behaviour change theory utilised). Although guidance for describing interventions [ 64 ] advises key aspects of context are included in reports, this may not include data on the full range of conditions that might be causally important, and review research teams may have limited knowledge of these ‘cases’ themselves. Second, less successful interventions are less likely to be published, potentially limiting the diversity of cases, particularly of cases with unsuccessful outcomes. A strength of QCA is the separate analysis of conditions leading to positive and negative outcomes: this is precluded where there is insufficient evidence on negative outcomes [ 50 ]. Third, when including a range of types of intervention, it can be unclear whether the cases included are truly comparable. A QCA study requires a high degree of theoretical and pragmatic case knowledge on the part of the researcher to calibrate conditions to qualitative anchors: it is reliant on deep understanding of complex contexts, and a familiarity with how conditions interact within and across contexts. Perhaps surprising is that only seven of the studies included here clearly drew on qualitative data, given that QCA is primarily seen as a method that requires thick, detailed knowledge of cases, particularly when the aim is to understand complex causation [ 8 ]. Whilst research teams conducting QCA in the context of systematic reviews may have detailed understanding in general of interventions within their spheres of expertise, they are unlikely to have this for the whole range of cases, particularly where a diverse set of contexts (countries, organisational settings) are included. Making a theoretical case for the valid comparability of such a case series is crucial. There may, then, be limitations in the portability of QCA methods for conducting studies entirely reliant on data from published evidence.

QCA was developed for small and medium N series of cases, and (as in the field more broadly, [ 61 ]), the samples in our studies predominantly had between 10 and 50 cases. However, there is increasing interest in the method as an alternative or complementary technique to regression-oriented statistical methods for larger samples [ 65 ], such as from surveys, where detailed knowledge of cases is likely to be replaced by theoretical knowledge of relationships between conditions (see [ 23 ]). The two larger N (> 100 cases) studies in our sample were an individual level analysis of survey data [ 46 , 47 ] and an analysis of intervention arms from a systematic review [ 50 ]. Larger sample sizes allow more conditions to be included in the analysis [ 23 , 26 ], although for evaluative research, where the aim is developing a causal explanation, rather than simply exploring patterns, there remains a limit to the number of conditions that can be included. As the number of conditions included increases, so too does the number of possible configurations, increasing the chance of unique combinations and of generating spurious solutions with a high level of consistency. As a rule of thumb, once the number of conditions exceeds 6–8 (with up to 50 cases) or 10 (for larger samples), the credibility of solutions may be severely compromised [ 23 ].

Strengths and weaknesses of the study

A systematic review has the potential advantages of transparency and rigour and, if not exhaustive, our search is likely to be representative of the body of research using QCA for evaluative public health research up to 2020. However, a limitation is the inevitable difficulty in operationalising a ‘public health’ intervention. Exclusions on scope are not straightforward, given that most social, environmental and political conditions impact on public health, and arguably a greater range of policy and social interventions (such as fiscal or trade policies) that have been the subject of QCA analyses could have been included, or a greater range of more clinical interventions. However, to enable a manageable number of papers to review, and restrict our focus to those papers that were most directly applicable to (and likely to be read by) those in public health policy and practice, we operationalised ‘public health interventions’ as those which were likely to be directly impacting on population health outcomes, or on behaviours (such as increased physical activity) where there was good evidence for causal relationships with public health outcomes, and where the primary research question of the study examined the conditions leading to those outcomes. This review has, of necessity, therefore excluded a considerable body of evidence likely to be useful for public health practice in terms of planning interventions, such as studies on how to better target smoking cessation [ 66 ] or foster social networks [ 67 ] where the primary research question was on conditions leading to these outcomes, rather than on conditions for outcomes of specific interventions. Similarly, there are growing number of descriptive epidemiological studies using QCA to explore factors predicting outcomes across such diverse areas as lupus and quality of life [ 68 ]; length of hospital stay [ 69 ]; constellations of factors predicting injury [ 70 ]; or the role of austerity, crisis and recession in predicting public health outcomes [ 71 ]. Whilst there is undoubtedly useful information to be derived from studying the conditions that lead to particular public health problems, these studies were not directly evaluating interventions, so they were also excluded.

Restricting our search to publications in English and to peer reviewed publications may have missed bodies of work from many regions, and has excluded research from non-governmental organisations using QCA methods in evaluation. As this is a rapidly evolving field, with relatively recent uptake in public health (all our included studies were after 2005), our studies may not reflect the most recent advances in the area.

Implications for conducting and reporting QCA studies

This systematic review has reviewed studies that deployed an emergent methodology, which has no reporting guidelines and has had, to date, a relatively low level of awareness among many potential evidence users in public health. For this reason, many of the studies reviewed were relatively detailed on the methods used, and the rationale for utilising QCA.

We did not assess quality directly, but used indicators of good practice discussed in QCA methodological literature, largely written for policy studies scholars, and often post-dating the publication dates of studies included in this review. It is also worth noting that, given the relatively recent development of QCA methods, methodological debate is still thriving on issues such as the reliability of causal inferences [ 72 ], alongside more general critiques of the usefulness of the method for policy decisions (see, for instance, [ 73 ]). The authors of studies included in this review also commented directly on methodological development: for instance, Thomas et al. suggests that QCA may benefit from methods development for sensitivity analyses around calibration decisions [ 42 ].

However, we selected quality criteria that, we argue, are relevant for public health research> Justifying the selection of cases, discussing and justifying the calibration of set membership, making data sets available, and reporting truth tables, consistency and coverage are all good practice in line with the usual requirements of transparency and credibility in methods. When QCA studies aim to provide explanation of outcomes (rather than exploring configurations), it is also vital that they are reported in ways that enhance the credibility of claims made, including justifying the number of conditions included relative to cases. Few of the studies published to date met all these criteria, at least in the papers included here (although additional material may have been provided in other publications). To improve the future discoverability and uptake up of QCA methods in public health, and to strengthen the credibility of findings from these methods, we therefore suggest the following criteria should be considered by authors and reviewers for reporting QCA studies which aim to provide causal evidence about the configurations of conditions that lead to implementation or outcomes:

The paper title and abstract state the QCA design;

The sampling unit for the ‘case’ is clearly defined (e.g.: patient, specified geographical population, ward, hospital, network, policy, country);

The population from which the cases have been selected is defined (e.g.: all patients in a country with X condition, districts in X country, tertiary hospitals, all hospitals in X country, all health promotion networks in X province, European policies on smoking in outdoor places, OECD countries);

The rationale for selection of cases from the population is justified (e.g.: whole population, random selection, purposive sample);

There are sufficient cases to provide credible coverage across the number of conditions included in the model, and the rationale for the number of conditions included is stated;

Cases are comparable;

There is a clear justification for how choices of relevant conditions (or ‘aspects of context’) have been made;

There is sufficient transparency for replicability: in line with open science expectations, datasets should be available where possible; truth tables should be reported in publications, and reports of coverage and consistency provided.

Implications for future research

In reviewing methods for evaluating natural experiments, Craig et al. focus on statistical techniques for enhancing causal inference, noting only that what they call ‘qualitative’ techniques (the cited references for these are all QCA studies) require “further studies … to establish their validity and usefulness” [ 2 ]. The studies included in this review have demonstrated that QCA is a feasible method when there are sufficient (comparable) cases for identifying configurations of conditions under which interventions are effective (or not), or are implemented (or not). Given ongoing concerns in public health about how best to evaluate interventions across complex contexts and systems, this is promising. This review has also demonstrated the value of adding QCA methods to the tool box of techniques for evaluating interventions such as public policies, health promotion programmes, and organisational changes - whether they are implemented in a randomised way or not. Many of the studies in this review have clearly generated useful evidence: whether this evidence has had more or less impact, in terms of influencing practice and policy, or is more valid, than evidence generated by other methods is not known. Validating the findings of a QCA study is perhaps as challenging as validating the findings from any other design, given the absence of any gold standard comparators. Comparisons of the findings of QCA with those from other methods are also typically constrained by the rather different research questions asked, and the different purposes of the analysis. In our review, QCA were typically used alongside other methods to address different questions, rather than to compare methods. However, as the field develops, follow up studies, which evaluate outcomes of interventions designed in line with conditions identified as causal in prior QCAs, might be useful for contributing to validation.

This review was limited to public health evaluation research: other domains that would be useful to map include health systems/services interventions and studies used to design or target interventions. There is also an opportunity to broaden the scope of the field, particularly for addressing some of the more intractable challenges for public health research. Given the limitations in the evidence base on what works to address inequalities in health, for instance [ 74 ], QCA has potential here, to help identify the conditions under which interventions do or do not exacerbate unequal outcomes, or the conditions that lead to differential uptake or impacts across sub-population groups. It is perhaps surprising that relatively few of the studies in this review included cases at the level of country or region, the traditional level for QCA studies. There may be scope for developing international comparisons for public health policy, and using QCA methods at the case level (nation, sub-national region) of classic policy studies in the field. In the light of debate around COVID-19 pandemic response effectiveness, comparative studies across jurisdictions might shed light on issues such as differential population responses to vaccine uptake or mask use, for example, and these might in turn be considered as conditions in causal configurations leading to differential morbidity or mortality outcomes.

When should be QCA be considered?

Public health evaluations typically assess the efficacy, effectiveness or cost-effectiveness of interventions and the processes and mechanisms through which they effect change. There is no perfect evaluation design for achieving these aims. As in other fields, the choice of design will in part depend on the availability of counterfactuals, the extent to which the investigator can control the intervention, and the range of potential cases and contexts [ 75 ], as well as political considerations, such as the credibility of the approach with key stakeholders [ 76 ]. There are inevitably ‘horses for courses’ [ 77 ]. The evidence from this review suggests that QCA evaluation approaches are feasible when there is a sufficient number of comparable cases with and without the outcome of interest, and when the investigators have, or can generate, sufficiently in-depth understanding of those cases to make sense of connections between conditions, and to make credible decisions about the calibration of set membership. QCA may be particularly relevant for understanding multiple causation (that is, where different configurations might lead to the same outcome), and for understanding the conditions associated with both lack of effect and effect. As a stand-alone approach, QCA might be particularly valuable for national and regional comparative studies of the impact of policies on public health outcomes. Alongside cluster randomised trials of interventions, or alongside systematic reviews, QCA approaches are especially useful for identifying core combinations of causal conditions for success and lack of success in implementation and outcome.

Conclusions

QCA is a relatively new approach for public health research, with promise for contributing to much-needed methodological development for addressing causation in complex systems. This review has demonstrated the large range of evaluation questions that have been addressed to date using QCA, including contributions to process evaluations of trials and for exploring the conditions leading to effectiveness (or not) in systematic reviews of interventions. There is potential for QCA to be more widely used in evaluative research, to identify the conditions under which interventions across contexts are implemented or not, and the configurations of conditions associated with effect or lack of evidence of effect. However, QCA will not be appropriate for all evaluations, and cannot be the only answer to addressing complex causality. For explanatory questions, the approach is most appropriate when there is a series of enough comparable cases with and without the outcome of interest, and where the researchers have detailed understanding of those cases, and conditions. To improve the credibility of findings from QCA for public health evidence users, we recommend that studies are reported with the usual attention to methodological transparency and data availability, with key details that allow readers to judge the credibility of causal configurations reported. If the use of QCA continues to expand, it may be useful to develop more comprehensive consensus guidelines for conduct and reporting.

Availability of data and materials

Full search strategies and extraction forms are available by request from the first author.

Abbreviations

Comparative Methods for Systematic Cross-Case Analysis

crisp set QCA

fuzzy set QCA

multi-value QCA

Medical Research Council

• Qualitative Comparative Analysis

randomised control trial

Physical Activity

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Acknowledgements

The authors would like to thank and acknowledge the support of Sara Shaw, PI of MR/S014632/1 and the rest of the Triple C project team, the experts who were consulted on the final list of included studies, and the reviewers who provided helpful feedback on the original submission.

This study was funded by MRC: MR/S014632/1 ‘Case study, context and complex interventions (Triple C): development of guidance and publication standards to support case study research’. The funder played no part in the conduct or reporting of the study. JG is supported by a Wellcome Trust Centre grant 203109/Z/16/Z.

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Hanckel, B., Petticrew, M., Thomas, J. et al. The use of Qualitative Comparative Analysis (QCA) to address causality in complex systems: a systematic review of research on public health interventions. BMC Public Health 21 , 877 (2021). https://doi.org/10.1186/s12889-021-10926-2

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Article contents

Comparison in qualitative research.

• Lesley Bartlett Lesley Bartlett University of Wisconsin–Madison
• , and  Frances Vavrus Frances Vavrus University of Minnesota
• https://doi.org/10.1093/acrefore/9780190264093.013.621
• Published online: 30 June 2020

Comparison is a valuable and widely touted analytical technique in social research, but different disciplines and fields have markedly different notions of comparison. There are at least two important logics for comparison. The first, the logic of juxtaposition, is guided by a neopositivist orientation. It uses a regularity theory of causation; it structures the study by defining cases, variables, and units of analysis a priori ; and it decontextualizes knowledge. The second, the logic of tracing, engages a realist theory of causation and examines how processes unfold, influenced by actors and the meanings they make, over time, in different locations, and at different scales. These two logics of comparison lead to distinct methodological techniques. However, with either logic of comparison, three dangers merit attention: decontextualization, commensurability, and ethnocentrism. One promising research heuristic that attends to different logics of comparison while avoiding these dangers is the comparative case study (CCS) approach. CCS entails three axes of comparison. The horizontal axis encourages comparison of how similar policies and practices unfold across sites at roughly the same level or scale, for example across a set of schools or across home, school, religious institution, and community organization. The vertical axis urges comparison across micro-, meso-, and macro-levels or scales. For example, a study of bilingual education in the United States should attend not only to homes, communities, classroom, and school dynamics (the micro-level), but also to meso-level district, state, and federal policies, as well as to factors influencing international mobility at the macro-level. Finally, the transversal axis, which emphasizes change over time, urges scholars to situate historically the processes or relations under consideration.

• qualitative methods
• comparative case studies
• epistemology
• horizontal comparison
• vertical comparison
• transversal comparison

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Qualitative comparative analysis

Wendy Olsen, CCSR/Social Statistics.

Video: Wendy Olsen

Qualitative comparative analysis by Wendy Olsen

What is qualitative comparative analysis? by Wendy Olsen

Qualitative Comparative Analysis (QCA) offers a new, systematic way of studying configurations of cases. QCA is used in comparative research and when using case-study research methods. The QCA analysts interprets the data qualitatively whilst also looking at causality between the variables. Thus the two-stage approach to studying causality has a qualitative first stage and a systematic second stage using QCA.

QCA is truly a mixed-methods approach to research. The basic data-handling mechanism is a simple qualitative table of data. This matrix is made up of rows and columns. Its column elements can be binary (yes/no), ordinal, or scaled index variates. QCA is best suited to small- to medium-N case-study projects with between 3 and 250 cases.

Crisp-set QCA uses only binary variates for its truth table. Fuzzy-set QCA also uses ordinal variates. A variate is a column of numbers representing real, not hypothetical, cases. In implementing QCA, one can code up the case-study data using NVIVO 7 software to create substantive case attributes. Multiple-level nested or non-nested cases can be handled. Fuzzy-set analysis is an optional extra stage, which also uses Boolean logic, but which is not necessary for QCA and tends not to be as qualitative as crisp-set QCA (csQCA) itself.

Experts at Manchester

• Dr Wendy Olsen , Senior Lecturer in Social Science Research Methods (SED) and in Socio-Economic Research (SOSS)
• Matthias Vom Hau, Brooks World Poverty Institute (now joined with the Institute for Development Policy and Management to become the Global Development Institute)

A research grant from the British Academy allowed Manchester University to host an Expert Roundtable on the Study of Strategies of Social Change using the Method of Qualitative Comparative Analysis (QCA) in 2008. Experts from Manchester University and the UK then visited Japan to hold a second roundtable there in 2009. A mixed-methods research training workshop took place on 15 June, 2010.

Key references

• Rihoux, B., & Ragin, C. C. (2009). Configurational comparative methods. Qualitative Comparative Analysis (QCA) and related techniques (Applied Social Research Methods). Thousand Oaks and London: Sage.
• Rihoux, B., and M. Grimm, eds. (2006). Innovative Comparative Methods For Policy Analysis: Beyond the quantitative-qualitative divide. New York, NY, Springer.
• Ragin, C.C. (2008). Redesigning social inquiry: Set relations in social research. Chicago: Chicago University Press.
• Ragin, C. C. (2000). Fuzzy-set social science. Chicago; London, University of Chicago Press. (One only needs to read the first half to cover QCA; the second half covers Fuzzy Set Analysis.)
• Byrne, D., and C. Ragin, eds. (2009), Handbook of Case-Centred Research Methods, London: Sage.
• QUAL-COMPARE email discussion list  - JISC email list about Qualitative Comparative Analysis
• Compasss  -  International network promoting small-N and medium-N comparative methods

Wendy Olsen offers software support and advice via both these web sites.

Staff interested in qualitative software Nvivo

• Dr. Rudolf Sinkovics  - Alliance Manchester Business School (AMBS), International Business
• Dr. Yanuar Nugroho  - formerly Alliance Manchester Business School (AMBS), Technological innovation
• Prof Cathy Cassell  - formerly Alliance Manchester Business School (AMBS), Qualitative methods in organisational research
• Dr. Richard Kyle  - Nursing, Midwifery and Social Work, Health and social geographer
• Dr. Sarah Kendal  - Nursing, Midwifery and Social Work, Emotional wellbeing interventions
• Dr. Ziv Amir  - Nursing, Midwifery and Social Work, Survivorship and cancer
• Dr Linda McGowan  - Nursing, Midwifery and Social Work, Women's health  
• Prof. Alys Young  - Nursing, Midwifery and Social Work, Social work research
• Wendy Olsen  - School of Social Sciences, Sociology of economic life
• Prof. Jennifer Mason  - Social Sciences, Kinship and family

Staff interested in qualitative software Atlas-TI

• Dr. Jane Griffiths  - Nursing, Midwifery and Social Work, Supportive and Palliative Care in Community Nursing
• Dr. Malcolm Campbell  - Nursing, Midwifery and Social Work, Statistics
• Prof. Christi Deaton  - Nursing, Midwifery and Social Work, Structural equation modelling and multi-level modelling
• Prof. Peter Callery  - Nursing, Midwifery and Social Work, Self care of long term conditions in childhood and young people

Download PDF slides of the presentation ' What is QCA? '

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• > The Case for Case Studies
• > Selecting Cases for Comparative Sequential Analysis

Book contents

• The Case for Case Studies
• Strategies for Social Inquiry
• Copyright page
• Contributors
• Preface and Acknowledgments
• 1 Using Case Studies to Enhance the Quality of Explanation and Implementation
• Part I Internal and External Validity Issues in Case Study Research
• Part II Ensuring High-Quality Case Studies
• 6 Descriptive Accuracy in Interview-Based Case Studies
• 7 Selecting Cases for Comparative Sequential Analysis
• 8 The Transparency Revolution in Qualitative Social Science
• Part III Putting Case Studies to Work: Applications to Development Practice

7 - Selecting Cases for Comparative Sequential Analysis

Novel Uses for Old Methods

from Part II - Ensuring High-Quality Case Studies

Published online by Cambridge University Press:  05 May 2022

Pavone analyzes how our evolving understanding of case-based causal inference via process-tracing should alter how we select cases for comparative inquiry. The chapter explicates perhaps the most influential and widely used means to conduct qualitative research involving two or more cases: Mill’s methods of agreement and difference. It then argues that the traditional use of Millian methods of case selection can lead us to treat cases as static units to be synchronically compared rather than as social processes unfolding over time. As a result, Millian methods risk prematurely rejecting and otherwise overlooking (1) ordered causal processes, (2) paced causal processes, and (3) equifinality, or the presence of multiple pathways that produce the same outcome. To address these issues, the chapter develops a set of recommendations to ensure the alignment of Millian methods of case selection with within-case sequential analysis.

7.1 Introduction

In the lead article of the first issue of Comparative politics , Harold Lasswell posited that the “scientific approach” and the “comparative method” are one and the same ( Reference Lasswell Lasswell 1968 : 3). So important is comparative case study research to the modern social sciences that two disciplinary subfields – comparative politics in political science and comparative-historical sociology – crystallized in no small part because of their shared use of comparative case study research ( Reference Collier and Finifter Collier 1993 ; Reference Adams, Clemens, Orloff, Adams, Clemens and Orloff Adams, Clemens, and Orloff 2005 : 22–26; Reference Mahoney and Thelen Mahoney and Thelen 2015 ). As a result, a first-principles methodological debate emerged about the appropriate ways to select cases for causal inquiry. In particular, the diffusion of econometric methods in the social sciences exposed case study researchers to allegations that they were “selecting on the dependent variable” and that “selection bias” would hamper the “answers they get” ( Reference Geddes Geddes 1990 ). Lest they be pushed to randomly select cases or turn to statistical and experimental approaches, case study researchers had to develop a set of persuasive analytic tools for their enterprise.

It is unsurprising, therefore, that there has been a profusion of scholarship discussing case selection over the years. Footnote 1 Reference Gerring and Cojocaru Gerring and Cojocaru (2015) synthesize this literature by deriving no less than five distinct types (representative, anomalous, most-similar, crucial, and most-different) and eighteen subtypes of cases, each with its own logic of case selection. It falls outside the scope of this chapter to provide a descriptive overview of each approach to case selection. Rather, the purpose of the present inquiry is to place the literature on case selection in constructive dialogue with the equally lively and burgeoning body of scholarship on process tracing ( Reference George and Bennett George and Bennett 2005 ; Reference Brady and Collier Brady and Collier 2010 ; Reference Beach and Pedersen Beach and Pedersen 2013 ; Reference Bennett and Checkel Bennett and Checkel 2015 ). I ask a simple question: Should our evolving understanding of causation and our toolkit for case-based causal inference courtesy of process-tracing scholars alter how scholars approach case selection? If so, why, and what may be the most fruitful paths forward?

To propose an answer, this chapter focuses on perhaps the most influential and widely used means to conduct qualitative research involving two or more cases: Mill’s methods of agreement and difference. Also known as the “most-different systems/cases” and “most-similar systems/cases” designs, these strategies have not escaped challenge – although, as we will see, many of these critiques were fallaciously premised on case study research serving as a weaker analogue to econometric analysis. Here, I take a different approach: I argue that the traditional use of Millian methods of case selection can indeed be flawed, but rather because it risks treating cases as static units to be synchronically compared rather than as social processes unfolding over time. As a result, Millian methods risk prematurely rejecting and otherwise overlooking (1) ordered causal processes, (2) paced causal processes, and (3) equifinality, or the presence of multiple pathways that produce the same outcome. While qualitative methodologists have stressed the importance of these processual dynamics, they have been less attentive to how these factors may problematize pairing Millian methods of case selection with within-case process tracing (e.g., Reference Hall, Mahoney and Rueschemeyer Hall 2003 ; Reference Tarrow Tarrow 2010 ; Reference Falleti, Mahoney, Mahoney and Thelen Falleti and Mahoney 2015 ). This chapter begins to fill that gap.

Taking a more constructive and prescriptive turn, the chapter provides a set of recommendations for ensuring the alignment of Millian methods of case selection with within-case sequential analysis. It begins by outlining how the deductive use of processualist theories can help reformulate Millian case selection designs to accommodate ordered and paced processes (but not equifinal processes). More originally, the chapter concludes by proposing a new, alternative approach to comparative case study research: the method of inductive case selection . By making use of Millian methods to select cases for comparison after a causal process has been identified within a particular case, the method of inductive case selection enables researchers to assess (1) the generalizability of the causal sequences, (2) the logics of scope conditions on the causal argument, and (3) the presence of equifinal pathways to the same outcome. In so doing, scholars can convert the weaknesses of Millian approaches into strengths and better align comparative case study research with the advances of processualist researchers.

Organizationally, the chapter proceeds as follows. Section 7.2 provides an overview of Millian methods for case selection and articulates how the literature on process tracing fits within debates about the utility and shortcomings of the comparative method. Section 7.3 articulates why the traditional use of Millian methods risks blinding the researcher to ordered, paced, and equifinal causal processes, and describes how deductive, processualist theorizing helps attenuate some of these risks. Section 7.4 develops a new inductive method of case selection and provides a number of concrete examples from development practice to illustrate how it can be used by scholars and policy practitioners alike. Section 7.5 concludes.

7.2 Case Selection in Comparative Research

7.2.1 case selection before the processual turn.

Before “process tracing” entered the lexicon of social scientists, the dominant case selection strategy in case study research sought to maximize causal leverage via comparison, particularly via the “methods of agreement and difference” of John Stuart Reference Mill Mill (1843 [1974] : 388–391).

In Mill’s method of difference, the researcher purposively chooses two (or more) cases that experience different outcomes, despite otherwise being very similar on a number of relevant dimensions. Put differently, the researcher seeks to maximize variation in the outcome variable while minimizing variation amongst a set of plausible explanatory variables. It is for this reason that the approach also came to be referred to as the ‘most-similar systems’ or ‘most-similar cases’ design – while Mill’s nomenclature highlights variation in the outcome of interest, the alternative terminology highlights minimal variation amongst a set of possible explanatory factors. The underlying logic of this case selection strategy is that because the cases are so similar, the researcher can subsequently probe for the explanatory factor that actually does exhibit cross-case variation and isolate it as a likely cause.

Mill’s method of agreement is the mirror image of the method of difference. Here, the researcher chooses two (or more) cases that experience similar outcomes despite being very different on a number of relevant dimensions. That is, the researcher seeks to minimize variation in the outcome variable while maximizing variation amongst a set of plausible explanatory variables. An alternative, independent variable-focused terminology for this approach was developed – the ‘most-different systems’ or ‘most-different cases’ design – breeding some confusion. The underlying logic of this case selection strategy is that it helps the researcher isolate the explanatory factor that is similar across the otherwise different cases as a likely cause. Footnote 2

Figure 7.1 Case selection setup under Mill’s methods of difference and agreement

Mill himself did not believe that such methods could yield causal inferences outside of the physical sciences ( Reference Mill Mill 1843 [1974] : 452). Nevertheless, in the 1970s a number of comparative social scientists endorsed Millian methods as the cornerstones of the comparative method. For example, Reference Przeworski and Teune Przeworski and Teune (1970) advocated in favor of the most-different cases design, whereas Reference Lijphart Lijphart (1971) favored the most-similar cases approach. In so doing, scholars sought case selection techniques that would be as analogous as possible to regression analysis: focused on controlling for independent variables across cases, maximizing covariation between the outcome and a plausible explanatory variable, and treating cases as a qualitative equivalent to a row of dataset observations. It is not difficult to see why this contributed to the view that case study research serves as the “inherently flawed” version of econometrics ( Reference Adams, Clemens, Orloff, Adams, Clemens and Orloff Adams, Clemens, and Orloff 2005 : 25; Reference Tarrow Tarrow 2010 ). Indeed, despite his prominence as a case study researcher, Reference Lijphart Lijphart (1975 : 165; Reference Lijphart 1971 : 685) concluded that “because the comparative method must be considered the weaker method,” then “if at all possible one should generally use the statistical (or perhaps even the experimental) method instead.” As Reference Hall, Mahoney and Rueschemeyer Hall (2003 : 380; 396) brilliantly notes, case study research

was deeply influenced by [Lijphart’s] framing of it … [where] the only important observations to be drawn from the cases are taken on the values of the dependent variable and a few explanatory variables … From this perspective, because the number of pertinent observations available from small-N comparison is seriously limited, the analyst lacks the degrees of freedom to consider more than a few explanatory variables, and the value of small-N comparison for causal inference seems distinctly limited.

In other words, the predominant case selection approach through the 1990s sought to do its best to reproduce a regression framework in a small-N setting – hence Lijphart’s concern with the “many variables, small number of cases” problem, which he argued could only be partially mitigated if, inter alia , the researcher increases the number of cases and decreases the number of variables across said cases ( Reference Lijphart 1971 : 685–686). Later works embraced Lijphart’s formulation of the problem even as they sought to address it: for example, Reference Eckstein, Greenstein and Polsby Eckstein (1975 : 85) argued that a “case” could actually be comprised of many “cases” if the unit of analysis shifted from being, say, the electoral system to, say, the voter. Predictably, such interventions invited retorts: Reference Lieberson Lieberson (1994) , for example, claimed that Millian methods’ inability to accommodate probabilistic causation, Footnote 3 interaction effects, and multivariate analysis would remain fatal flaws.

7.2.2 Enter Process Tracing

It is in this light that ‘process tracing’ – a term first used by Reference Hobarth Hobarth (1972) but popularized by Reference George and Lauren George (1979 ) and particularly Reference George and Bennett George and Bennett (2005) , Reference Brady and Collier Brady and Collier (2010) , Reference Beach and Pedersen Beach and Pedersen (2013) , and Reference Bennett and Checkel Bennett and Checkel (2015) – proved revolutionary for the ways in which social scientists conceive of case study research. Cases have gradually been reconceptualized not as dataset observations but as concatenations of concrete historical events that produce a specific outcome ( Reference Mahoney Goertz and Mahoney 2012 ). That is, cases are increasingly treated as social processes, where a process is defined as “a particular type of sequence in which the temporally ordered events belong to a single coherent pattern of activity” ( Reference Falleti, Mahoney, Mahoney and Thelen Falleti and Mahoney 2015 : 214). Although there exist multiple distinct conceptions of process tracing – from Bayesian approaches ( Reference Bennett, Bennett and Checkel Bennett 2015 ) to set-theoretic approaches ( Reference Mahoney, Kimball and Koivu Mahoney et al. 2009 ) to mechanistic approaches ( Reference Beach and Pedersen Beach and Pedersen 2013 ) to sequentialist approaches ( Reference Falleti, Mahoney, Mahoney and Thelen Falleti and Mahoney 2015 ) – their overall esprit is the same: reconstructing the sequence of events and interlinking causal logics that produce an outcome – isolating the ‘causes of effects’ – rather than probing a variable’s mean impact across cases via an ‘effects of causes’ approach. Footnote 4

For this intellectual shift to occur, processualist social scientists had to show how a number of assumptions underlying Millian comparative methods – as well as frequentist approaches more generally – are usually inappropriate for case study research. For example, the correlational approach endorsed by Reference Przeworski and Teune Przeworski and Teune (1970) , Reference Lijphart Lijphart (1971) , and Reference Eckstein, Greenstein and Polsby Eckstein (1975) treats observational units as homogeneous and independent ( Reference Hall, Mahoney and Rueschemeyer Hall 2003 : 382; Reference Mahoney Goertz and Mahoney 2012 ). Unit homogeneity means that “different units are presumed to be fully identical to each other in all relevant respects except for the values of the main independent variable,” such that each observation contributes equally to the confidence we have in the accuracy and magnitude of our causal estimates ( Reference Brady and Collier Brady and Collier 2010 : 41–42). Given this assumption, more observations are better – hence, Reference Lijphart Lijphart (1971) ’s dictum to “increase the number of cases” and, in its more recent variant, to “increase the number of observations” ( Reference King, Keohane and Verba King, Keohane, and Verba 1994 : 208–230). By independence, we mean that “for each observation, the value of a particular variable is not influenced by its value in other observations”; thus, each observation contributes “new information about the phenomenon in question” ( Reference Brady and Collier Brady and Collier 2010 : 43).

By contrast, practitioners of process tracing have shown that treating cases as social processes implies that case study observations are often interdependent and derived from heterogeneous units ( Reference Mahoney Goertz and Mahoney 2012 ). Unit heterogeneity means that not all historical events, and the observable evidence they generate, are created equal. Hence, some observations may better enable the reconstruction of a causal process because they are more proximate to the central events under study. Correlatively, this is why historians accord greater ‘weight’ to primary than to secondary sources, and why primary sources concerning actors central to a key event are more important than those for peripheral figures ( Reference Trachtenberg Trachtenberg 2009 ; Reference Tansey Tansey 2007 ). In short, while process tracing may yield a bounty of observable evidence, we seek not to necessarily increase the number, but rather the quality, of observations. Finally, by interdependence we mean that because time is “fateful” ( Reference Sewell Sewell 2005 : 6), antecedent events in a sequence may influence subsequent events. This “fatefulness” has multiple sources. For instance, historical institutionalists have shown how social processes can exhibit path dependencies where the outcome of interest becomes a central driver of its own reproduction ( Reference Pierson Pierson 1996 ; Reference Pierson Pierson 2000 ; Reference Mahoney Mahoney 2000 ; Reference Hall, Mahoney and Rueschemeyer Hall 2003 ; Reference Falleti, Mahoney, Mahoney and Thelen Falleti and Mahoney 2015 ). At the individual level, processual sociologists have noted that causation in the social world is rarely a matter of one billiard ball hitting another, as in Reference Hume Hume’s (1738 [2003]) frequentist concept of “constant conjunction.” Rather, it hinges upon actors endowed with memory, such that the micro-foundations of social causation rest on individuals aware of their own historicality ( Reference Sewell Sewell 2005 ; Reference Abbott Abbott 2001 ; Reference Abbott 2016 ).

At its core, eschewing the independence and unit homogeneity assumptions simply means situating case study evidence within its spatiotemporal context ( Reference Hall, Mahoney and Rueschemeyer Hall 2003 ; Reference Falleti and Lynch Falleti and Lynch 2009 ). This commitment is showcased by the language which process-sensitive case study researchers use when making causal inferences. First, rather than relating ‘independent variables’ to ‘dependent variables’, they often privilege the contextualizing language of relating ‘events’ to ‘outcomes’ ( Reference Falleti, Mahoney, Mahoney and Thelen Falleti and Mahoney 2015 ). Second, they prefer to speak not of ‘dataset observations’ evocative of cross-sectional analysis, but of ‘causal process observations’ evocative of sequential analysis ( Reference Brady and Collier Brady and Collier 2010 ; Reference Mahoney Goertz and Mahoney 2012 ). Third, they may substitute the language of ‘causal inference via concatenation’ – a terminology implying that unobservable causal mechanisms are embedded within a sequence of observable events – for that of ‘causal inference via correlation’, evocative of the frequentist billiard-ball analogy ( Reference Waldner and Kincaid Waldner 2012 : 68). The result is that case study research is increasingly hailed as a “distinctive approach that offers a much richer set of observations, especially about causal processes, than statistical analyses normally allow” ( Reference Hall, Mahoney and Rueschemeyer Hall 2003 : 397).

7.3 Threats to Processual Inference and the Role of Theory

While scholars have shown how process-tracing methods have reconceived the utility of case studies for causal inference, there remains some ambiguity about the implications for case selection, particularly using Millian methods. While several works have touched upon this theme (e.g., Reference Hall, Mahoney and Rueschemeyer Hall 2003 ; Reference George and Bennett George and Bennett 2005 ; Reference Levy Levy 2008 ; Reference Tarrow Tarrow 2010 ), the contribution that most explicitly wrestles with this topic is Reference Falleti, Mahoney, Mahoney and Thelen Falleti and Mahoney (2015) , who acknowledge that “the application of Millian methods for sequential arguments has not been systematically explored, although we believe it is commonly used in practice” ( Reference Falleti, Mahoney, Mahoney and Thelen Falleti and Mahoney 2015 : 226). Falleti and Mahoney argue that process tracing can remedy the weaknesses of Millian approaches: “When used in isolation, the methods of agreement and difference are weak instruments for small-N causal inference … small-N researchers thus normally must combine Millian methods with process tracing or other within-case methods to make a positive case for causality” ( Reference Falleti, Mahoney, Mahoney and Thelen 2015 : 225–226). Their optimism about the synergy between Millian methods and process tracing leads them to conclude that “by fusing these two elements, the comparative sequential method merits the distinction of being the principal overarching methodology for [comparative-historical analysis] in general” ( Reference Falleti, Mahoney, Mahoney and Thelen 2015 : 236).

Falleti and Mahoney’s contribution is the definitive statement of how comparative case study research has long abandoned its Lijphartian origins and fully embraced treating cases as social processes. It is certainly true that process-tracing advocates have shown that some past critiques of Millian methods may not have been as damning as they first appeared. For example, Reference Lieberson Lieberson’s (1994) critique that Millian case selection requires a deterministic understanding of causation has been countered by set-theoretic process tracers who note that causal processes can indeed be conceptualized as concatenations of necessary and sufficient conditions ( Reference Mahoney Goertz and Mahoney 2012 ; Reference Mahoney and Vanderpoel Mahoney and Vanderpoel 2015 ). After all, “at the individual case level, the ex post (objective) probability of a specific outcome occurring is either 1 or 0” ( Reference Mahoney Mahoney 2008 : 415). Even for those who do not explicitly embrace set-theoretic approaches and prefer to perform a series of “process tracing tests” (such as straw-in-the-wind, hoop, smoking gun, and doubly-decisive tests), the objective remains to evaluate the deterministic causal relevance of a historical event on the next linkage in a sequence ( Reference Collier Collier 2011 ; Reference Mahoney Mahoney 2012 ). In this light, Millian methods appear to have been thrown a much-needed lifeline.

Yet processualist researchers have implicitly exposed new, and perhaps more damning, weaknesses in the traditional use of the comparative method. Here, Reference Falleti, Mahoney, Mahoney and Thelen Falleti and Mahoney (2015) are less engaged in highlighting how their focus on comparing within-case sequences should push scholars to revisit strategies for case selection premised on assumptions that process-tracing advocates have undermined. In this light, I begin by outlining three hitherto underappreciated threats to inference associated with the traditional use of Millian case selection: potentially ignoring (1) ordered and (2) paced causal processes, and ignoring (3) the possibility of equifinality. I then demonstrate how risks (1) and (2) can be attenuated deductively by formulating processualist theories and tweaking Millian designs for case selection.

Risk 1: Ignoring Ordered Processes

Process-sensitive social scientists have long noted that “the temporal order of the events in a sequence [can be] causally consequential for the outcome of interest” ( Reference Falleti, Mahoney, Mahoney and Thelen Falleti and Mahoney 2015 : 218; see also Reference Pierson Pierson 2004 : 54–78). For example, where individual acts of agency play a critical role – such as political elites’ response to a violent protest – “reordering can radically change [a] subject’s understanding of the meaning of particular events,” altering their response and the resulting outcomes ( Reference Abbott Abbott 1995 : 97).

An evocative illustration is provided by Reference Sewell Sewell’s (1996) analysis of how the storming of the Bastille in 1789 produced the modern concept of “revolution.” After overrunning the fortress, the crowd freed the few prisoners held within it; shot, stabbed, and beheaded the Bastille’s commander; and paraded his severed head through the streets of Paris ( Reference Sewell Sewell 1996 : 850). When the French National Assembly heard of the taking of the Bastille, it first interpreted the contentious event as “disastrous news” and an “excess of fury”; yet, when the king subsequently responded by retreating his troops to their provincial barracks, the Assembly recognized that the storming of the Bastille had strengthened its hand, and proceeded to reinterpret the event as a patriotic act of protest in support of political change ( Reference Sewell Sewell 1996 : 854–855). The king’s reaction to the Bastille thus bolstered the Assembly’s resolve to “invent” the modern concept of revolution as a “legitimate rising of the sovereign people that transformed the political system of a nation” ( Reference Sewell Sewell 1996 : 854–858). Proceeding counterfactually, had the ordering of events been reversed – had the king withdrawn his troops before the Bastille had been stormed – the National Assembly would have had little reason to interpret the popular uprising as a patriotic act legitimating reform rather than a violent act of barbarism.

Temporal ordering may also alter a social process’s political outcomes through macro-level mechanisms. For example, consider Reference Falleti Falleti’s (2005 , Reference Falleti 2010 ) analysis of the conditions under which state decentralization – the devolution of national powers to subnational administrative bodies – increases local political autonomy in Latin America. Through process tracing, Falleti demonstrates that when fiscal decentralization precedes electoral decentralization, local autonomy is increased, since this sequence endows local districts with the monetary resources necessary to subsequently administer an election effectively. However, when the reverse occurs, such that electoral decentralization precedes fiscal decentralization, local autonomy is compromised. For although the district is being offered the opportunity to hold local elections, it lacks the monetary resources to administer them effectively, endowing the national government with added leverage to impose conditions upon the devolution of fiscal resources.

For our purposes, what is crucial to note is not simply that temporal ordering matters, but that in ordered processes it is not the presence or absence of events that is most consequential for the outcome of interest. For instance, in Falleti’s analysis both fiscal and electoral decentralization occur. This means that a traditional Millian framework risks dismissing some explanatory events as causally irrelevant on the grounds that their presence is insufficient for explicating the outcome of interest (see Figure 7.2 ).

Figure 7.2 How ordered processes risk being ignored by a Millian setup

The way to deductively attenuate the foregoing risk is to develop an ordered theory and then modify the traditional Millian setup to assess the effect of ordering on an outcome of interest. That is, deductive theorizing aimed at probing the causal effect of ordering can guide us in constructing an appropriate Millan case selection design, such as that in Figure 7.3 . In this example, we redefine the fourth independent variable to measure not the presence or absence of a fourth event, but rather to measure the ordering of two previously defined events (in this case, events 1 and 2). This case selection setup would be appropriate if deductive theorizing predicts that the outcome of interest is produced when event 1 is followed by event 2 (such that, unless this specific ordering occurs, the presence of events 1 and 2 is insufficient to generate the outcome). In other words, if Millian methods are to be deductively used to select cases for comparison, the way to guard against prematurely dismissing the causal role of temporal ordering is to explicitly theorize said ordering a priori . If this proves difficult, or if the researcher lacks sufficient knowledge to develop such a theory, it is advisable to switch to the more inductive method for case selection outlined in the next section .

Figure 7.3 Deductively incorporating ordered processes within a Millian setup

Risk 2: Ignoring Paced Processes

Processualist researchers have also emphasized that, beyond temporal order, “the speed or duration of events … is causally consequential” ( Reference Falleti, Mahoney, Mahoney and Thelen Falleti and Mahoney 2015 : 219). For example, social scientists have long distinguished an “eventful temporality” ( Reference Sewell Sewell 1996 ) from those “big, slow moving” incremental sequences devoid of rapid social change ( Reference Pierson, Mahoney and Rueschemeyer Pierson 2003 ). For historical institutionalists, this distinction is illustrated by “critical junctures” – defined as “relatively short periods of time during which there is a substantially heightened probability that agents’ choices will affect the outcome of interest” ( Reference Capoccia and Kelemen Capoccia and Kelemen 2007 : 348; Reference Capoccia, Mahoney and Thelen Capoccia 2015 : 150–151) – on the one hand, and those “causal forces that develop over an extended period of time,” such as “cumulative” social processes, sequences involving “threshold effects,” and “extended causal chains” on the other hand ( Reference Pierson Pierson 2004 : 82–90; Reference Mahoney, Thelen, Mahoney and Thelen Mahoney and Thelen 2010 ).

An excellent illustration is provided by Reference Beissinger Beissinger (2002) ’s analysis of the contentious events that led to the collapse of the Soviet State. Descriptively, the sequence of events has its origins in the increasing transparency of Soviet institutions and freedom of expression accompanying Gorbachev’s Glasnost ( Reference Beissinger Beissinger 2002 : 47). As internal fissures within the Politburo began to emerge in 1987, Glasnost facilitated media coverage of the split within the Soviet leadership ( Reference Beissinger 2002 : 64). In response, “interactive attempts to contest the state grew regularized and began to influence one another” ( Reference Beissinger 2002 : 74). These challenging acts mobilized around previously dormant national identities, and for the first time – often out of state incompetence – these early protests were not shut down ( Reference Beissinger 2002 : 67). Protests reached a boiling point in early 1989 as the first semicompetitive electoral campaign spurred challengers to mobilize the electorate and cultivate grievances in response to regime efforts to “control nominations and electoral outcomes” ( Reference Beissinger 2002 : 86). By 1990 the Soviet State was crumbling, and “in many parts of the USSR demonstration activity … had become a normal means for dealing with political conflict” ( Reference Beissinger 2002 : 90).

Crucially, Beissinger stresses that to understand the causal dynamics of the Soviet State’s collapse, highlighting the chronology of events is insufficient. The 1987–1990 period comprised a moment of “thickened history” wherein “what takes place … has the potential to move history onto tracks otherwise unimaginable … all within an extremely compressed period of time” ( Reference Beissinger 2002 : 27). Information overload, the density of interaction between diverse social actors, and the diffusion of contention engendered “enormous confusion and division within Soviet institutions,” allowing the hypertrophy of challenging acts to play “an increasingly significant role in their own causal structure” ( Reference Beissinger 2002 : 97, 27). In this light, the temporal compression of a sequence of events can bolster the causal role of human agency and erode the constraints of social structure. Proceeding counterfactually, had the exact same sequence of contentious events unfolded more slowly, it is doubtful that the Soviet State would have suddenly collapsed.

Many examples of how the prolongation of a sequence of events can render them invisible, and thus produce different outcomes, could be referenced. Consider, for example, how global climate change – which is highlighted by Reference Pierson Pierson (2004 : 81) as a prototypical process with prolonged time horizons – conditions the psychological response of social actors. As a report from the American Psychological Association underscores, “climate change that is construed as rapid is more likely to be dreaded,” for “people often apply sharp discounts to costs or benefits that will occur in the future … relative to experiencing them immediately” ( Reference Swim Swim et al. 2009 : 24–25; Reference Loewenstein and Elster Loewenstein and Elster 1992 ). This logic is captured by the metaphor of the “boiling frog”: “place a frog in a pot of cool water, and gradually raise the temperature to boiling, and the frog will remain in the water until it is cooked” ( Reference Boyatzis Boyatzis 2006 : 614).

What is important to note is that, once more, paced processes are not premised on the absence or presence of their constitutive events being causally determinative; rather, they are premised on the duration of events (or their temporal separation) bearing explanatory significance. Hence the traditional approach to case selection risks neglecting the causal impact of temporal duration on the outcome of interest (see Figure 7.4 ).

Figure 7.4 Paced processes risk being ignored by a Millian setup

Here, too, the way to deductively assess the causal role of pacing on an outcome of interest is to explicitly develop a paced theory before selecting cases for empirical analysis. On the one hand, we might theorize that it is the duration of a given event that is causally consequential; on the other hand, we might theorize that it is the temporal separation of said event from other events that is significant. Figure 7.5 suggests how a researcher can assess both theories through a revised Millian design. In the first example, we define a fourth independent variable measuring not the presence of a fourth event, but rather the temporal duration of a previously defined event (in this case, event 1). This would be an appropriate case selection design to assess a theory predicting that the outcome of interest occurs when event 1 unfolds over a prolonged period of time (such that if event 1 unfolds more rapidly, its mere occurrence is insufficient for the outcome). In the second example, we define a fourth independent variable measuring the temporal separation between two previously defined events (in this case, events 1 and 2). This would be an appropriate case selection design for a theory predicting that the outcome of interest only occurs when event 1 is temporally distant to event 2 (such that events 1 and 2 are insufficient for the outcome if they are proximate). Again, if the researcher lacks a priori knowledge to theorize how a paced process may be generating the outcome, it is advisable to adopt the inductive method of case selection described in Section 7.4 .

Figure 7.5 Deductively incorporating paced processes within a Millian setup

Risk 3: Ignoring Equifinal Causal Processes

Finally, researchers have noted that causal processes may be mired by equifinality: the fact that “multiple combinations of values … produce the same outcome” ( Reference Mahoney Mahoney 2008 : 424; see also Reference George and Bennett George and Bennett 2005 ; Reference Mahoney Goertz and Mahoney 2012 ). More formally, set-theoretic process tracers account for equifinality by emphasizing that, in most circumstances, “necessary” conditions or events are actually INUS conditions – individually necessary components of an unnecessary but sufficient combination of factors ( Reference Mahoney and Vanderpoel Mahoney and Vanderpoel 2015 : 15–18).

One of the reasons why processualist social scientists increasingly take equifinality seriously is the recognition that causal mechanisms may be context-dependent. Sewell’s work stresses that “the consequences of a given act … are not intrinsic to the act but rather will depend on the nature of the social world within which it takes place” ( Reference Sewell Sewell 2005 : 9–10). Similarly, Reference Falleti and Lynch Falleti and Lynch (2009 : 2; 11) argue that “causal effects depend on the interaction of specific mechanisms with aspects of the context within which these mechanisms operate,” hence the necessity of imposing “scope conditions” on theory building. One implication is that the exact same sequence of events in two different settings may produce vastly different causal outcomes. The flip side of this conclusion is that we should not expect a given outcome to always be produced by the same sequence of events.

For example, consider Sewell’s critique of Reference Skocpol Skocpol (1979) ’s States and Social Revolutions for embracing an “experimental temporality.” Skocpol deploys Millian methods of case selection to theorize that the great social revolutions – the French, Russian, and Chinese revolutions – were caused by a conjunction of three necessary conditions: “(1) military backwardness, (2) politically powerful landlord classes, and (3) autonomous peasant communities” ( Reference Sewell Sewell 2005 : 93). Yet to permit comparison, Skocpol assumes that the outcomes of one revolution, and the processes of historical change more generally, have no effect on a subsequent revolution ( Reference Sewell Sewell 2005 : 94–95). This approach amounts to “cutting up the congealed block of historical time into artificially interchangeable units,” ignoring the fatefulness of historical sequences ( Reference Sewell Sewell 2005 ). For example, the Industrial Revolution “intervened” between the French and Russian Revolutions, and consequently one could argue that “the revolt of the Petersburg and Moscow proletariat was a necessary condition for social revolution in Russia in 1917, even if it was not a condition for the French Revolution in 1789” ( Reference Sewell Sewell 2005 : 94–95). What Sewell is emphasizing, in short, is that peasant rebellion is an INUS condition (as is a proletariat uprising), rather than a necessary condition.

Another prominent example of equifinality is outlined by Reference Collier Collier’s (1999 : 5–11) review of the diverse pathways through which democratization occurs. In the elite-driven pathway, emphasized by Reference O’Donnell and Schmitter O’Donnell and Schmitter (1986 ), an internal split amongst authoritarian incumbents emerges; this is followed by liberalizing efforts by some incumbents, which enables the resurrection of civil society and popular mobilization; finally, authoritarian incumbents negotiate a pacted transition with opposition leaders. By contrast, in the working-class-driven pathway, emphasized by Reference Rueschemeyer, Stephens and Stephens Rueschemeyer, Stephens, and Stephens (1992) , a shift in the material balance of power in favor of the democracy-demanding working class and against the democracy-resisting landed aristocracy causes the former to overpower the latter, and via a democratic revolution from below a regime transition occurs. Crucially, Reference Collier Collier (1999 : 12) emphasizes that these two pathways need not be contradictory (or exhaustive): the elite-driven pathway appears more common in the Latin American context during the second wave of democratization, whereas the working-class-driven pathway appears more common in Europe during the first wave of democratization.

What is crucial is that Millian case selection is premised on there being a single cause underlying the outcome of interest. As a result, Millian methods risk dismissing a set of events as causally irrelevant ex ante in one case simply because that same set of events fails to produce the outcome in another case (see Figure 7.6 ). Unlike ordered and paced processes, there is no clear way to leverage deductive theorizing to reconfigure Millian methods for case selection and accommodate equifinality. However, I argue that the presence of equifinal pathways can be fruitfully probed if we embrace a more inductive approach to comparative case selection, as the next section outlines.

Figure 7.6 Equifinal causal processes risk being ignored by a Millian setup

7.4 A New Approach: The Method of Inductive Case Selection

If a researcher wishes to guard against ignoring consequential temporal dynamics but lacks the a priori knowledge necessary to develop a processual theory and tailor their case selection strategy, is there an alternative path forward? Yes, indeed: I suggest that researchers could wield most-similar or most-different cases designs to (1) probe causal generalizability, (2) reveal scope conditions, and (3) explore the presence of equifinality. Footnote 5 To walk through this more inductive case selection approach, I engage some case studies from development practice to illustrate how researchers and practitioners alike could implement and benefit from the method.

7.4.1 Tempering the Deductive Use of Millian Methods

To begin, one means to ensure against a Millian case selection design overlooking an ordered, paced, or equifinal causal process (in the absence of deductive theorizing) is to be wary of leveraging the methods of agreement and difference to eliminate potential explanatory factors ( Reference Falleti, Mahoney, Mahoney and Thelen Falleti and Mahoney 2015 : 225–226). That is, the decision to discard an explanatory variable or historical event as causally unnecessary (via the method of agreement) or insufficient (via the method of difference) may be remanded to the process-tracing stage, rather than being made ex ante at the case selection stage.

Notice how this recommendation is particularly intuitive in light of the advances in process-tracing methods. Before this burgeoning literature existed, Millian methods were called upon to accomplish two things at once: (1) provide a justification for selecting two or more cases for social inquiry, and (2) yield causal leverage via comparison and the elimination of potential explanatory factors as unnecessary or insufficient. But process-tracing methodologists have showcased how the analysis of temporal variation disciplined via counterfactual analysis, congruence testing, and process-tracing tests renders within-case causal inference possible even in the absence of an empirical comparative case ( Reference George and Bennett George and Bennett 2005 ; Reference Gerring Gerring 2007 ; Reference Collier Collier 2011 ; Reference Mahoney Mahoney 2012 ; Reference Beach and Pedersen Beach and Pedersen 2013 ; Reference Bennett and Checkel Bennett and Checkel 2015 ; Reference Levy Levy 2015 ). That is, the ability to make causal inferences need not be primarily determined at the case selection stage.

The foregoing implies that if a researcher does not take temporal dynamics into account when developing their theory, the use of Millian methods should do no more than to provisionally discount the explanatory purchase of a given explanatory factor. The researcher should then bear in mind that as the causal process is reconstructed from a given outcome, the provisionally discounted factor may nonetheless be shown to be of causal relevance – particularly if the underlying process is ordered or paced, or if equifinal pathways are possible.

Despite these limitations, Millian methods might fruitfully serve additional functions from the standpoint of case selection, particularly if researchers shift (1) when and (2) why they make use of them. First, Millian methods may be as – if not more – useful after process tracing of a particular case is completed rather than to set the stage for within-case analysis. Such a chronological reversal – process tracing followed by Millian case selection, instead of Millian case selection followed by process tracing – inherently embraces a more inductive, theory-building approach to case study research ( Reference Falleti, Mahoney, Mahoney and Thelen Falleti and Mahoney 2015 : 229–231) which, I suspect, is far more commonly used in practice than is acknowledged. I refer to this approach as the method of inductive case selection , wherein “theory-building process tracing” ( Reference Beach and Pedersen Beach and Pedersen 2013 : 16–18) of a single case is subsequently followed by the use of a most-similar or most-different cases design.

7.4.2 Getting Started: Selecting the Initial Case

The method of inductive case selection begins by assuming that the researcher has justifiable reasons for picking a particular case for process tracing and is subsequently looking to contextualize the findings or build a theory outwards. Hence, the first step involves picking an initial case. Qualitative methodologists have already supplied a number of plausible logics for selecting a single case, and I describe three nonexhaustive possibilities here: (1) theoretical or historical importance; (2) policy relevance and salience; and (3) empirically puzzling nature.

First, an initial case may be selected due to its theoretical or historical importance. Reference Eckstein, Greenstein and Polsby Eckstein (1975) , for example, defines an idiographic case study as a case where the specific empirical events/outcome serve as a central referent for a scholarly literature. As an illustration, Reference Gerring and Cojocaru Gerring and Cojocaru (2015 : 11) point to Reference North and Weingast North and Weingast (1989) ’s influential study of how the Glorious Revolution in seventeenth-century Britain favorably shifted the constitutional balance of power for the government to make credible commitments to protecting property rights (paving the way for the financial revolution of the early eighteenth century). Given that so much of the scholarly debate amongst economic historians centers on the institutional foundations of economic growth, North and Weingast’s case study was “chosen (it would appear) because of its central importance in the [historical political economy] literature on the topic, and because it is … a prominent and much-studied case” ( Reference Gerring and Cojocaru Gerring and Cojocaru 2015 : 11). In other words, Reference North and Weingast North and Weingast (1989) ’s study is idiographic in that it “aim[s] to explain and/or interpret a single historical episode,” but it remains “theory-guided” in that it “focuses attention on some theoretically specified aspects of reality and neglects others” ( Reference Levy Levy 2008 : 4).

While the causes of the Glorious Revolution are a much-debated topic amongst economic historians, they have less relevance to researchers and practitioners focused on assessing the effects of contemporary public policy interventions. Hence, a second logic for picking a first case for process tracing is its policy relevance and salience. Reference George and Bennett George and Bennett (2005 : 263–286) define a policy-relevant case study as one where the outcome is of interest to policy-makers and its causes are at least partially amenable to policy manipulation. For example, one recent World Bank case study ( Reference El-Saharty and Nagaraj El-Saharty and Nagaraj 2015 ) analyzes how HIV/AIDS prevalence amongst vulnerable subpopulations – particularly female sex workers – can be reduced via targeted service delivery. To study this outcome, two states in India – Andhra Pradesh and Karnataka – were selected for process tracing. There are three reasons why this constitutes an appropriate policy-relevant case selection choice. First, the outcome of interest – a decline in HIV/AIDS prevalence amongst female sex workers – was present in both Indian states. Second, because India accounts for almost 17.5 percent of the world population and has a large population of female sex workers, this outcome was salient to the government ( Reference El-Saharty and Nagaraj El-Saharty and Nagaraj 2015 : 3). Third, the Indian government had created a four-phase National AIDS Control Program (NACP) spanning from 1986 through 2017, meaning that at least one set of possible explanatory factors for the decline in HIV/AIDS prevalence comprised policy interventions that could be manipulated. Footnote 6

A third logic for picking an initial case for process tracing is its puzzling empirical nature. One obvious instantiation is when an exogenous shock or otherwise significant event/policy intervention yields a different outcome from the one scholars and practitioners expected. Footnote 7 For example, in 2004 the federal government of Nigeria partnered with the World Bank to improve the share of Nigeria’s urban population with access to piped drinking water. This partnership – the National Urban Water Sector Reform Project (NUWSRP1) – aimed to “increase access to piped water supply in selected urban areas by improving the reliability and financial viability of selected urban water utilities” and by shifting resources away from “infrastructure rehabilitation” that had failed in the past ( Reference Hima and Santibanez Hima and Santibanez 2015 : 2). Despite $200 million worth of investments, ultimately the NUWSRP1 “did not perform as strongly on the institutional reforms needed to ensure sustainability” ( Reference Hima and Santibanez Hima and Santibanez 2015 ). Given this puzzling outcome, the World Bank conducted an intensive case study to ask why the program did “not fully meet its essential objective of achieving a sustainable water delivery service” ( Reference Hima and Santibanez Hima and Santibanez 2015 ). Footnote 8

The common thread of these three logics for selecting an initial case is that the case itself is theoretically or substantively important and that its empirical dynamics – underlying either the outcome itself or its relationship to some explanatory events – are not well understood. That being said, the method of inductive case selection merely presumes that there is some theoretical, policy-related, empirical, or normative justification to pick the initial case.

7.4.3 Probing Generalizability Via a Most-Similar Cases Design

It is after picking an initial case that the method of inductive case selection contributes novel guidelines for case study researchers by reconfiguring how Millian methods are used. Namely, how should one (or more) additional cases be selected for comparison, and why? This question presumes that the researcher wishes to move beyond an idiographic, single-case study for the purposes of generating inferences that can travel. Yet in this effort, we should take seriously process-tracing scholars’ argument that causal mechanisms are often context-dependent. As a result, the selection of one or more comparative cases is not meant to uncover universally generalizable abstractions; rather, it is meant to contextualize the initial case within a set or family of cases that are spatiotemporally bounded.

That being said, the first logical step is to understand whether the causal inferences yielded by the process-traced case can indeed travel to other contexts ( Reference Goertz Goertz 2017 : 239). This constitutes the first reconfiguration of Millian methods: the use of comparative case studies to assess generalizability. Specifically, after within-case process tracing reveals a factor or sequence of factors as causally important to an outcome of interest, the logic is to select a case that is as contextually analogous as possible such that there is a higher probability that the causal process will operate similarly in the second case. This approach exploits the context-dependence of causal mechanisms to the researcher’s advantage: Similarity of context increases the probability that a causal mechanism will operate similarly across both cases. By “context,” it is useful to follow Reference Falleti and Lynch Falleti and Lynch (2009 : 14) and to be

concerned with a variety of contextual layers: those that are quite proximate to the input (e.g., in a study of the emergence of radical right-wing parties, one such layer might be the electoral system); exogenous shocks quite distant from the input that might nevertheless effect the functioning of the mechanism and, hence, the outcome (e.g., a rise in the price of oil that slows the economy and makes voters more sensitive to higher taxes); and the middle-range context that is neither completely exogenous nor tightly coupled to the input and so may include other relevant institutions and structures (the tax system, social solidarity) as well as more atmospheric conditions, such as rates of economic growth, flows of immigrants, trends in partisan identification, and the like.

For this approach to yield valuable insights, the researcher focuses on ‘controlling’ for as many of these contextual explanatory factors (crudely put, for as many independent variables) as possible. In other words, the researcher selects a most-similar case: if the causal chain similarly operates in the second case, this would support the conclusion that the causal process is likely at work across the constellation of cases bearing ‘family resemblances’ to the process-traced case ( Reference Soifer Soifer 2020 ). Figure 7.7 displays the logic of this design:

Figure 7.7 Probing generalizability by selecting a most-similar case

As in Figure 7.7 , suppose that process tracing of Case 1 reveals that some sequence of events (in this example, event 4 followed by event 5) caused the outcome of interest. The researcher would then select a most-similar case (a case with similar values/occurrences of other independent variables/events (here, IV1–IV3) that might also influence the outcome). The researcher would then scout whether the sequence in Case 1 (event 4 followed by event 5) also occurs in the comparative case. If it does, the expectation for a minimally generalizable theory is that it would produce a similar outcome in Case 2 as in Case 1. Correlatively, if the sequence does not occur in Case 2, the expectation is that it would not experience the same outcome as Case 1. These findings would provide evidence that the explanatory sequence (event 4 followed by event 5) has causal power that is generalizable across a set of cases bearing family resemblances.

For example, suppose a researcher studying democratization in Country A finds evidence congruent with the elite-centric theory of democratization of Reference O’Donnell and Schmitter O’Donnell and Schmitter (1986 ) described previously. To assess causal generalizability, the researcher would subsequently select a case – Country B – that is similar in the background conditions that the literature has shown to be conducive to democratization, such as level of GDP per capita ( Reference Przeworski and Limongi Przeworski and Limongi 1997 ; Reference Boix and Stokes Boix and Stokes 2003 ) or belonging to the same “wave” of democratization via spatial and temporal proximity ( Reference Collier, Rustow and Erickson Collier 1991 ; Reference Huntington Huntington 1993 ). Notice that these background conditions in Case B have to be at least partially exogenous to the causal process whose generalizability is being probed – that is, they cannot constitute the events that directly comprise the causal chain revealed in Case A. One way to think about them is as factors that in Case A appear to have been necessary, but less proximate and important, conditions for the outcome. Here, importance is determined by the “extent that they are [logically/counterfactually] present only when the outcome is present” ( Reference Mahoney, Kimball and Koivu Mahoney et al. 2009 : 119), whereas proximity is determined by the degree to which the condition is “tightly coupled” with the chain of events directly producing the outcome ( Reference Falleti, Mahoney, Mahoney and Thelen Falleti and Mahoney 2015 : 233).

An example related to the impact of service delivery in developmental contexts can be drawn from the World Bank’s case study of HIV/AIDS interventions in India. Recall that this case study actually spans across two states: Andhra Pradesh and Karnataka. In a traditional comparative case study setup, the selection of both cases would seem to yield limited insights. After all, they are contextually similar: “Andhra Pradesh and Karnataka … represent the epicenter of the HIV/AIDS epidemic in India. In addition, they were early adopters of the targeted interventions”; and they also experience a similar outcome: “HIV/AIDS prevalence among female sex workers declined from 20 percent to 7 percent in Andhra Pradesh and from 15 percent to 5 percent in Karnataka between 2003 and 2011” ( Reference El-Saharty and Nagaraj El-Saharty and Nagaraj 2015 : 7; 3). In truth, this comparative case study design makes substantial sense: had the researchers focused on the impact of the Indian government’s NACP program only in Andhra Pradesh or only in Karnataka, one might have argued that there was something unique about either state that rendered it impossible to generalize the causal inferences. By instead demonstrating that favorable public health outcomes can be traced to the NACP program in both states, the researchers can support the argument that the intervention would likely prove successful in other contexts to the extent that they are similar to Andhra Pradesh and Karnataka.

One risk of the foregoing approach is highlighted by Reference Sewell Sewell (2005 : 95–96): contextual similarity may suggest cross-case interactions that hamper the ability to treat the second, most-similar case as if it were independent of the process-traced case. For example, an extensive body of research has underscored how protests often diffuse across proximate spatiotemporal contexts through mimicry and the modularity of repertoires of contention ( Reference Tilly Tilly 1995 ; Reference Tarrow Tarrow 1998 ). And, returning to the World Bank case study of HIV/AIDS interventions in Andhra Pradesh and Karnataka, one concern is that because these states share a common border, cross-state learning or other interactions might limit the value-added of a comparative design over a single case study, since the second case may not constitute truly new data. The researcher should be highly sensitive to this possibility when selecting and subsequently process tracing the most-similar case: the greater the likelihood of cross-case interactions, the lesser the likelihood that it is a case-specific causal process – as opposed to cross-case diffusion mechanism – that is doing most of the explanatory work.

Conversely, if the causal chain is found to operate differently in the second, most-similar case, then the researcher can make an argument for rejecting the generalizability of the causal explanation with some confidence. The conclusion would be that the causal process is sui generis and requires the “localization” of the theoretical explanation for the outcome of interest ( Reference Tarrow Tarrow 2010 : 251–252). In short, this would suggest that the process-traced case is an exceptional or deviant case, given a lack of causal generalizability even to cases bearing strong family resemblances. Here, we are using the ‘strong’ notion of ‘deviant’: the inability of a causal process to generalize to similar contexts substantially decreases the likelihood that “other cases” could be explained with reference to (or even in opposition to) the process-traced case.

There is, of course, the risk that by getting mired in the weeds of the first case, the researcher is unable to recognize how the overall chronology of events and causal logics in the most-similar case strongly resembles the process-traced case. That is, a null finding of generalizability in a most-similar context calls on the researcher to probe whether they have descended too far down the “ladder of generality,” requiring more abstract conceptual categories to compare effectively ( Reference Sartori Sartori 1970 ; Reference Collier and Levitsky Collier and Levitsky 1997 ).

7.4.4 Probing Scope Conditions and Equifinality Via a Most-Different Cases Design

A researcher that has process-traced a given case and revealed a factor or sequence of factors as causally relevant may also benefit from leveraging a most-different cases approach. This case selection technique yields complementary insights to the most-similar cases design described in the previous section , but its focus is altogether different: instead of uncovering the degree to which an identified causal process travels, the objective is to try to understand where and why it fails to travel and whether alternative pathways to the same outcome may be possible.

More precisely, by selecting a case that differs substantially from the process-traced case in background characteristics, the researcher maximizes contextual heterogeneity and the likelihood that the causal process will not generalize to the second case ( Reference Soifer Soifer 2020 ). Put differently, the scholar would be selecting a least-likely case for generalizability, because the context-dependence of causal mechanisms renders it unlikely that the same sequence of events will generate the same outcome in the second case. This would offer a first cut at establishing “scope conditions” upon the generalizability of the theory ( Reference Tarrow Tarrow 2010 : 251) by isolating which contextual factors prevented the process from producing the outcome in the most-different case.

Figure 7.8 provides a visual illustration of what this design could look like. Suppose, once more, that process tracing in Case 1 has revealed that some event 4 followed by event 5 generated the outcome of interest. To maximize the probability that we will be able to place scope conditions on this finding, we would select a comparative case that is most different to the process-traced case (a case with different values/occurrences of other independent variables/events [denoted as IV1–IV3 in Figure 7.8 ] that might also influence the outcome) but which also experienced the sequence of event 4 followed by event 5. Given the contextual differences between these two cases, the likelihood that the same sequence will produce the same outcome in both is low, which then opens up opportunities for the researcher to probe the logic of scope conditions. In this endeavor, temporality can serve as a useful guide: a means for restricting the set of potential contextual factors that prevented the causal process from reproducing the outcome in Case 2 is to identify at what chronological point the linkages between events 4 and 5 on the one hand and the outcome of interest on the other hand branched off from the way they unfolded in Case 1. The researcher can then scout which contextual factors exuded the greatest influence at that temporal location and identify them as central to the scope conditions to be placed upon the findings.

Figure 7.8 Probing scope conditions by selecting a most-different case

To provide an example for how this logic of inquiry can work, consider a recent case study focused on understanding the effectiveness of Mexico’s conditional cash transfer program – Opportunitades , the first program of its kind – in providing monetary support to the female heads of Indigenous households ( Reference Alva Estrabridis and Ortega Nieto Alva Estrabridis and Ortega Nieto 2015 ). The program suffered from the fact that Indigenous beneficiaries dropped out at higher rates than their non-Indigenous counterparts. In 2009 the World Bank spearheaded an Indigenous Peoples Plan (IPP) to bolster service delivery of cash transfers to Indigenous populations, which crucially included “catering to indigenous peoples in their native languages and disseminating information in their languages” ( Reference Alva Estrabridis and Ortega Nieto Alva Estrabridis and Ortega Nieto 2015 : 2). A subsequent impact evaluation found that “[w]hen program messages were offered in beneficiaries’ mother tongues, they were more convincing, and beneficiaries tended to participate and express themselves more actively” ( Reference Alva Estrabridis and Ortega Nieto Alva Estrabridis and Ortega Nieto 2015 ; Reference Mir, Gámez, Loyola, Martí and Veraza Mir et al. 2011 ).

Researchers might well be interested in the portability of the foregoing finding, in which case the previously described most-similar cases design is appropriate – for example, a comparison with the Familias en Accion program in Colombia may be undertaken ( Reference Attanasio, Battistin, Fitzsimons, Mesnard and Vera-Hernandez. Attanasio et al. 2005 ). But they might also be interested in the limits of the policy intervention – in understanding where and why it is unlikely to yield similar outcomes. To assess the scope conditions upon the “bilingualism” effect of cash transfer programs, a most-different cases design is appropriate. Thankfully, conditional cash transfer programs are increasingly common even in historical, cultural, and linguistic contexts markedly different from Mexico, most prominently in sub-Saharan Africa ( Reference Lagarde, Haines and Palmer Lagarde et al. 2007 ; Reference Garcia and Moore Garcia and Moore 2012 ). Selecting a comparative case from sub-Saharan Africa should prove effective for probing scope conditions: the more divergent the contextual factors, the less likely it is that the policy intervention will produce the same outcome in both contexts.

On the flip side, in the unlikely event that part or all of the causal process is nonetheless reproduced in the most-different case, the researcher would obtain a strong signal that they have identified one of those rare causal explanations of general scope. In coming to this conclusion, however, the researcher should be wary of “conceptual stretching” ( Reference Sartori Sartori 1970 : 1034), such that there is confidence that the similarity in the causal chain across the most-different cases lies at the empirical level and is not an artificial by-product of imprecise conceptual categories ( Reference Bennett and Checkel Bennett and Checkel 2015 : 10–11). Here process tracing, by pushing researchers to not only specify a sequence of “tightly-coupled” events ( Reference Falleti, Mahoney, Mahoney and Thelen Falleti and Mahoney 2015 : 233), but also to collect observable implications about the causal mechanisms concatenating these events, can guard against conceptual stretching. By opening the “black box” of causation through detailed within-case analysis, process tracing limits the researcher’s ability to posit “pseudo-equivalences” across contexts ( Reference Sartori Sartori 1970 : 1035).

Selecting a most-different case vis-à-vis the process-traced case is also an excellent strategy for probing equifinality – for maximizing the likelihood that the scholar will be able to probe multiple causal pathways to the same outcome. To do so, it is not sufficient to merely ensure divergence in background conditions; it is equally necessary to follow Mill’s method of agreement by ensuring that the outcome in the process-traced case is also present in the second, most-different case. By ensuring minimal variation in outcome, the scholar guarantees that process tracing the second case will lead to the desired destination; by ensuring maximal variation in background conditions, the scholar substantially increases the likelihood that process tracing will reveal a slightly or significantly different causal pathway to said destination. Should an alternative route to the outcome be found, then its generalizability could be assessed using the most-similar cases approach described previously.

Figure 7.9 visualizes what this case selection design might look like. Here, as in previous examples, suppose process tracing in Case 1 provides evidence that event 4 followed by event 5 produced the outcome of interest. The researcher then selects a case with the same outcome, but with different values/occurrences of some independent variables/events (in this case, IV1–IV3) that may influence the outcome. Working backwards from the outcome to reconstruct the causal chain that produced it, the researcher then probes whether (i) the sequence (event 4 followed by event 5) also occurred in Case 2, and (ii) whether the outcome of interest can be retraced to said sequence. Given the contextual dissimilarities between these most-different cases, such a finding is rather unlikely, which would subsequently enable to the researcher to probe whether some other factor (perhaps IV2/event 2 in the example of Figure 7.9 ) produced the outcome in the comparative case instead, which would comprise clear evidence of equifinality.

Figure 7.9 Probing equifinality by selecting a most-different case with the same outcome

To return to the concrete example of Mexico’s conditional cash transfer program’s successful outreach to marginalized populations via bilingual service provision, an alternative route to the same outcome might be unearthed if a cash transfer program without bilingual outreach implemented in a country characterized by different linguistic, gender, and financial decision-making norms proves similarly successful in targeting marginalized populations. Several factors – including recruitment procedures, the size of the cash transfers, the requirements for participation, and the supply of other benefits ( Reference Lagarde, Haines and Palmer Lagarde et al. 2007 : 1902) – could interact with the different setting to produce similar intervention outcomes, regardless of whether multilingual services are provided. Such a finding would suggest that these policy interventions can be designed in multiple ways and still prove effective.

To conclude, the method of inductive case selection complements within-case analysis by supplying a coherent logic for probing generalizability, scope conditions, and equifinality. To summarize, Figure 7.10 provides a roadmap of this approach to comparative case selection.

Figure 7.10 Case selection roadmap to assess generalizability, scope conditions, equifinality

In short, if the researcher has the requisite time and resources, a multistage use of Millian methods to conduct four comparative case studies could prove very fertile. The researcher would begin by selecting a second, most-similar case to assess causal generalizability to a family of cases similar to the process-traced case; subsequently, a third, most-different case would be selected to surface possible scope conditions blocking the portability of the theory to divergent contexts; and a fourth, most-different case experiencing the same outcome would be picked to probe equifinal pathways. This sequential, four-case comparison would substantially improve the researcher’s ability to map the portability and contours of both their empirical analysis and their theoretical claims. Footnote 9

7.5 Conclusion

The method of inductive case selection converts process tracing meant to simply “craft a minimally sufficient explanation of a particular outcome” into a methodology used to build and refine a causal theory – a form of “theory-building process-tracing” ( Reference Beach and Pedersen Beach and Pedersen 2013 : 16–18). Millian methods are called upon to probe the portability of a particular causal process or causal mechanism and to specify the logics of its relative contextual-dependence. In so doing, they enable theory-building without presuming that the case study researcher holds the a priori knowledge necessary to account for complex temporal dynamics at the deductive theorizing stage. Both of these approaches – deductive, processualist theorizing on the one hand, and the method of inductive case selection on the other hand – provide some insurance against Millian methods leading the researcher into ignoring the ordered, paced, or equifinal structure that may underlie the pathway(s) to the outcome of interest. But, I would argue, the more inductive approach is uniquely suited for research that is not only process-sensitive, but also open to novel insights supplied by the empirical world that may not be captured by existing theories.

Furthermore, case study research often does (and should!) proceed with the scholar outlining why an outcome is of interest, and then seeking ways to not only make inferences about what produced said outcome (via process tracing) but situating it within a broader empirical and theoretical landscape (via the method of inductive case selection). This approach pushes scholars to answer that pesky yet fundamental question – why should we care or be interested in this case/outcome? – before disciplining their drive for generalizable causal inferences. After all, the deductive use of Millian methods tells us nothing about why we should care about the cases selected, yet arguably this is an essential component of any case selection justification. By deploying a most-similar or most-different cases design after an initial case has been justifiably selected due to its theoretical or historical importance, policy relevance, or puzzling empirical nature, the researcher is nudged toward undertaking case study research yielding causal theories that are not only comparatively engaged, but also substantively interesting.

The method of inductive case selection is most useful when the foregoing approach constitutes the esprit of the case study researcher. Undoubtedly, deductively oriented case study research (see Reference Lieberman Lieberman 2005 ; Reference Lieberman, Mahoney and Thelen 2015 ) and traditional uses of Millian methods will continue to contribute to social scientific understanding. Nevertheless, the perils of ignoring important sequential causal dynamics – particularly in the absence of good, processualist theories – should caution researchers to proceed with the greatest of care. In particular, researchers should be willing to revise both theory building and research design to its more inductive variant should process tracing reveal temporal sequences that eschew the analytic possibilities of the traditional comparative method.

I would like to thank Jennifer Widner and Michael Woolcock for the invitation to write this chapter, and Daniel Ortega Nieto for pointing me to case studies conducted by the World Bank’s Global Delivery Initiative that I use as illustrative examples, as well as Jack Levy, Hillel Soifer, Andrew Moravcsik, Cassandra Emmons, Rory Truex, Dan Tavana, Manuel Vogt, and Killian Clarke for constructive feedback.

1 See, for example, Reference Przeworski and Teune Przeworski and Teune (1970) , Reference Lijphart Lijphart (1971) , Reference Eckstein, Greenstein and Polsby Eckstein (1975) , Reference Yin Yin (1984) , Reference Geddes Geddes (1990) , Reference Collier and Finifter Collier (1993) , Reference Faure Faure (1994) , Reference George and Bennett George and Bennett (2005) , Reference Flyvbjerg Flyvbjerg (2006) , Reference Levy Levy (2008) , Reference Seawright and Gerring Seawright and Gerring (2008) , Reference Gerring Gerring (2007) , Reference Brady and Collier Brady and Collier (2010) , and Reference Tarrow Tarrow (2010) .

2 Some scholars, such as Reference Faure Faure (1994) , distinguish Mill’s dependent-variable driven methods of agreement and difference from the independent-variable driven most-similar and most-different systems designs, suggesting they are distinct. But because, as Figure 7.1 shows, Mill’s dependent-variable driven methods also impose requirements on the array of independent variables to permit causal inference via exclusion, this distinction is not particularly fertile.

3 In Mill’s method of difference, factors present in both cases are eliminated for being insufficient for the outcome (in the method of agreement, factors that vary across the cases are eliminated for being unnecessary).

4 Note that Mill himself distinguished between deductively assessing the average “effect of causes” and inductively retracing the “causes of effects” using the methods of agreement and disagreement ( Reference Mill Mill 1843 [1974] , pp. 449, 764).

5 The proposed approach bears several similarities to Reference Soifer Soifer’s (2020) fertile analysis of how “shadow cases” in comparative research can contribute to theory-building and empirical analysis.

6 This study found that the expansion of clinical services into government facilities embedded in the public health system, the introduction of peer educators, and the harmonization of large quantities of public health data underlay the timing and breadth of the decline in HIV/AIDS amongst female sex workers.

7 What Reference Levy Levy (2008 :13) calls a “deviant” case – which “focus[es] on observed empirical anomalies in existing theoretical propositions” – would also fit within the category of a puzzling case.

8 Process tracing revealed that a conjunction of factors – management turnover and a lackluster culture of staff performance at the state level, inadequate coordination at the federal level, premature disbursement of funds, and citizen aversion to the commercialization of the public water supply – underlay the initially perplexing underperformance of the urban water delivery project.

9 Many thanks to Rory Truex for highlighting this implication of the roadmap in Figure 7.5 .

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• Selecting Cases for Comparative Sequential Analysis
• By Tommaso Pavone
• Edited by Jennifer Widner , Princeton University, New Jersey , Michael Woolcock , Daniel Ortega Nieto
• Book: The Case for Case Studies
• Online publication: 05 May 2022
• Chapter DOI: https://doi.org/10.1017/9781108688253.008

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• Open access
• Published: 11 September 2024

Implementing peer support into practice in mental health services: a qualitative comparative case study

• Steve Gillard 1 ,
• Rhiannon Foster 1 ,
• Sarah White 2 ,
• Rahul Bhattacharya 3 ,
• Paul Binfield 3 ,
• Rachel Eborall 4 ,
• Sarah L Gibson 5 ,
• Daniella Harnett 3 ,
• Alan Simpson 6 ,
• Mike Lucock 7 ,
• Jacqueline Marks 8 ,
• Julie Repper 9 ,
• Miles Rinaldi 10 , 11 ,
• Anthony Salla 1 &
• Jessica Worner 12  

BMC Health Services Research volume  24 , Article number:  1050 ( 2024 ) Cite this article

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Metrics details

Peer workers are people with personal experience of mental distress, employed within mental health services to support others with similar experiences. Research has identified a range of factors that might facilitate or hinder the introduction of new peer worker roles into mental health services. While there is mixed evidence for the effectiveness of peer worker delivered interventions, there are no studies exploring how implementation might be associated with effect.

This was a qualitative comparative case study using data from interviews with 20 peer workers and their five supervisors. Peer workers delivered peer support for discharge from inpatient to community mental health care as part of a randomised controlled trial. In the trial, level of participant engagement with peer support was associated with better outcome (hospital readmission). Study sites with higher levels of engagement also had higher scores on a measure of fidelity to peer support principles. We compared data from sites with contrasting levels of engagement and fidelity using an analytical framework derived from implementation theory.

In high engagement-high fidelity sites, there was regular work with clinical teams preparing for working alongside peer workers, and a positive relationship between staff on inpatient wards and peer workers. The supervisor role was well resourced, and delivery of peer support was highly consistent with the intervention manual. In low engagement-low fidelity sites peer workers were employed in not-for-profit organisations to support people using public mental health services and in rural areas. Supervisors faced constrained resources and experienced barriers to joint working between organisations. In these sites, peer workers could experience challenging relationships with ward staff. Issues of geography and capacity limited opportunities for supervision and team-building, impacting consistency of delivery.

Conclusions

This study provides clear indication that implementation can impact delivery of peer support, with implications for engagement and, potentially, outcomes of peer worker interventions. Resourcing issues can have knock-on effects on consistency of delivery, alongside challenges of access, authority and relationship with clinical teams, especially where peer workers were employed in not-for-profit organisations. Attention needs to be paid to the impact of geography on implementation.

Trial registration

ISRCTN registry number ISRCTN10043328, registered 28 November 2016.

Peer Review reports

Peer support in mental health services

People with personal experience of mental distress, often referred to as peer workers, are increasingly employed within mental health services internationally to support others with similar experiences. An extensive literature explores a range of implementation issues that might dilute the distinctive qualities of peer support when introduced into public mental health services [ 1 , 2 ]. These include adequate provision of role specific training for PWs, [ 3 , 4 ] support and supervision for PWs, [ 5 ] clarity of expectation around the way in which PWs bring experience-based knowledge to mental healthcare, [ 2 . 6 ] and preparation of clinical teams to work alongside PWs [ 7 ]. It has been argued that ‘over-professionalisation’ or ‘institutionalisation’ of the PW role constrains the distinctive contribution of peer support [ 8 , 9 , 10 , 11 ].

Trials of peer support in mental health services continue to demonstrate inconsistent results, with some studies indicating that peer support might be superior to care-as-usual or a comparator intervention, [ 12 , 13 ] while others indicate no difference in effect [ 14 , 15 ]. Some of this variation might be explained by heterogeneity of interventions, population or outcome, but it is also possible that the quality of implementation of peer support into mental healthcare settings is associated with the effect of peer support interventions [ 16 , 17 ].

It has been noted that peer support is often poorly described in the trial literature, [ 17 , 18 ] with a lack of research assessing association between implementation and outcome. A recent review of one-to-one peer support in mental health services categorised peer support as being well implemented where at least two of the following criteria were reported: dedicated peer support training; clear description of the underlying processes of peer support; well-defined support structures for PWs (e.g. supervision) [ 19 ]. However, only a small number of studies reported sufficient data to conduct an analysis and results were unclear. There is a need for research that explicitly considers the possible relationship between quality of implementation and the outcomes of peer support.

Implementation theory

Implementation science offers a range of frameworks for understanding the facilitators and barriers to successful implementation of healthcare innovation into practice [ 20 ]. There is a clear recognition that the effects of any intervention will always depend on successful implementation [ 21 ]. The well-established Promoting Action on Research Implementation in Health Services (PARIHS) framework conceptualises successful implementation of research-based innovation into healthcare in terms of the nature of the evidence on which the innovation is based, the context or environment into which the innovation is placed, and the method by which implementation is facilitated [ 22 ]. In recent years, the co-design [ 23 ] or coproduction [ 24 ] of new interventions in mental health has gained prominence, with people who use mental health services bringing experience-based knowledge to the process, alongside the professional and practice-based knowledge brought by healthcare professionals. Given that this experiential knowledge is core to peer support, and that a number of members of the research term brought their own experiences of mental distress and/ or of using mental health services to the design and conduct of the research, we adapted the PARIHS framework for the purposes of this study. An earlier scoping review of implementation literature and an empirical case study, [ 25 ] undertaken by members of the team (SG and RF), identified five domains where experiential knowledge might impact research implementation, and we mapped these domains directly onto the framework (Table  1 ).

The ENRICH trial

A trial of peer support for discharge from inpatient to community mental health care indicated that peer support was not superior to care-as-usual (follow up by community mental health services within seven days of discharge) in terms of either the primary outcome – readmission within 12 months of discharge – or a range of secondary outcomes [ 26 ]. PWs received eight days of training focused on individual strengths and connecting to community, met the people they were supporting at least once while still inpatients and then weekly for up to four months post-discharge. Peer support was flexible and collaborative, informed by a peer support principles framework [ 27 ]. PWs received group and individual supervision from an experienced peer worker coordinator (PWC) who had access to an action learning set with other PWCs across study sites. The trial and intervention are described in detail in a protocol paper [ 28 ].

Findings from the trial indicated that 62.5% of participants offered peer support had at least two contacts with their PW, at least one of which was post-discharge, and that those participants were significantly less likely to be readmitted than a similar group of PWs in the care-as-usual group [ 26 ]. There might be many reasons why people chose not to, or were unable to engage with their PW, including the possibility that peer support was not always well implemented into practice in the trial.

This paper aims to explore if and how levels of engagement in a new peer support intervention were associated with implementation of the intervention, and therefore how implementation of peer support in mental health services might be optimised in the future.

Study design

We take a comparative case study approach, informed by case-orientated Qualitative Comparative Analysis [ 29 ] and pattern-matching [ 30 ] techniques, considering the seven sites where the study took place as cases. Sites were National Health Services (NHS) mental health trusts (public healthcare provider organisations) in England, where the new peer support intervention was delivered as part of the ENRICH trial. Sites were selected to provide contrast in urban, town and rural localities, geographical spread across England, and where mental health trusts were committed to introducing new PW roles into mental health services. In most sites PWs were directly employed by the mental health trust, while in others a much smaller, voluntary (not-for-profit) sector organisation was sub-contracted by the trust to employ PWs to provide support to people using mental health trust services. Information about each site is given in Table  2 below.

To inform case selection for the comparative analysis we charted level of engagement at each site – percentage of trial participants offered peer support who had at least two contacts with their PW, at least one of which was post-discharge – against site fidelity score, measured using an index designed to assess fidelity of delivery of peer support at site level against a set of principles articulating what is distinctive about peer support compared to other forms of mental health support [ 31 ] (Fig.  1 ). Fidelity was assessed through a semi-structured interview with PWs, the people they supported and their supervisor, rated by researchers against criteria based on the principles framework. A high fidelity score indicates that peer support had been implemented according to those principles. Fidelity was assessed after peer support had been delivered for at least six months at each site.

Relationship between engagement with peer support and fidelity

Figure  1 is indicative of a direct relationship between engagement with peer support and fidelity, offering rationale for selecting sites with higher or lower levels of both engagement and fidelity as cases for comparative analysis. There was one outlier, site 2, where fidelity was high (11) but engagement was mid-range (51%). We included this site in the comparative analysis as engagement might be explained by implementation issues not related to fidelity of delivery.

We report on the Evidence domain of the framework in a paper describing how experiential knowledge was central to developing the ENRICH peer support intervention [ 32 ]. Our research questions here are based on the Context and Facilitation domains of the framework, with context referring largely to the NHS Trust in which implementation took place (question 1), and facilitators being the PWs and PWCs who delivered the peer support (questions 2–4):

How did the culture of organisations, leadership (including issues of access and authority ) and monitoring and feedback impact implementation of peer support?

How did PWs and PWCs feel that their roles were characterised?

How did PWs and PWCs feel they were able to exercise flexibility while remaining consistent in their approach to delivering peer support?

How did experiential knowledge underpin peer support as it was delivered at each site?

Data sources

Peer worker interviews. Thirty-two PWs delivered peer support in the ENRICH trial and were invited to give written informed consent to participate in the research. All 32 consented and were interviewed after 12 months of delivering peer support. Interviews explored how well training prepared them for the role, their experiences of working as a PW, the support they received in the role and their relationship with clinical teams they worked alongside.

Peer worker coordinator interviews. Eight PWCs supervised PWs in the trial. Seven PWCs were themselves experienced PWs and one was a mental health nurse who shared the role with an experienced PW. All 8 PWCs gave informed consent to participate in the research and were interviewed at the same timepoint as PWs. Interviews explored PWCs’ experiences of supporting PWs, how well they thought the role was supported and organisational issues impacting delivery of peer support.

Interviews were conducted by researchers working from a perspective of having experienced mental distress and/ or having used mental health services, and played a key role in schedule development. Interview schedules can be found in the Supplementary Material file.

Data analysis

Interviews were audio-recorded, pseudonymised at the point of collection and transcribed verbatim.

Interview data were analysed using a framework approach [ 33 ] based on the Context and Facilitation domains of the modified PARIHS framework (see Table  1 ). Data were first coded to the constructs within those domains, with inductive space retained to code factors not related to the framework that participants described as impacting delivery of peer support. Second, a comparative, cross-case analysis was used to look for patterns of implementation that were: A, shared across cases; B, characterised high fidelity-high engagement cases; C, characterised low fidelity-low engagement cases; D, described implementation in the outlier case [ 30 ]. Preliminary analyses were undertaken by the first author and refined through iterative rounds of discussion with the whole team.

Characteristics of included cases

The two high engagement-high fidelity cases (sites 3,5), and the outlier high fidelity-low engagement case (site 2), were in urban areas with PWs directly employed in mental health NHS Trusts (see Table  2 ). The two low engagement-low fidelity cases (sites 4,6) were in areas that were a mix of rural localities with small towns or urban localities respectively. In both the latter sites PWs were employed by voluntary sector organisations outside of the NHS.

Characteristics of participants

A total of 20 PWs were included in the analysis, five each from sites 3 and 4, three each from sites 2 and 5, and two from site 6. Twelve PWs were female, seven were male and one preferred not to say. Three PWs were aged under 35 years of age, 12 aged from 35 to 55 years, one over 55 and four preferred not to say. Eleven PWs were White British, two were White Irish, one White other, one Black/ Black British, one Asian/ Asian British, one Arab, one Mixed White Asian with two preferring not to say.

There were five PWCs, one from each site. Four PWCs were female and one was male; two were aged from 35 to 55 and three over 55; all were White British.

Participant quotes presented below are identified with a site code (e.g. S1 = site 1) and role identifier (PW = Peer Worker; PWC = Peer Worker Coordinator) plus an additional number to distinguish between PWs at each site.

Implementation across cases

A number of implementation features were evident across all five cases, including characterisation of the PW role as largely consistent with the principles that were used to inform development of the intervention; [ 27 , 32 ] taking a non-judgemental approach and sharing experiences to create a safe space, make connections and build relationships:

‘We’re not going to be judgemental so to speak. It’s a safe place really for people to be themselves regardless of what their mental health issues are or mental health diagnoses are.’ (S5PW2). ‘I’m always sharing lived experience, whether that’s just generally or whether that’s personally with mental health … obviously you share when appropriate but you try to match that experience together so you have something in common, and then there is that mutuality and reciprocity and creating that trusting relationship.’ (S3PW3).

On the whole, training – as specified in the ENRICH manual – was consistently delivered and worked well to provide PWs with the range of skills they felt they needed for the role:

‘We did a lot about strengths-based approaches and I think that’s really informed the way that I interact with people, so I think I’m always trying to bring it back to what can you do, what is strong for you … we did a lot about active listening and also about discussing difficult issues … I think it’s been very helpful the stuff we did in training … definitely the boundaries and relationships sessions that we did …’ (S3PW1).

The importance of group supervision facilitated by the PWC, as well as individual supervision where required (both specified in the handbook), was indicated across sites, providing the opportunity for PWs to share experiences and receive feedback from one another as well as from the PWC:

‘I will hold these feelings until supervision and that’s when I let it out, offload it to my colleagues. And it’s been great because we’ve been bouncing it off each other and I’ve noticed that it’s not just me that was going through it, so it’s such a relief …’ (S2PW2). ‘… [PWC] will always ask how I am, if anything has triggered me or anything like that and she’s quite easy to talk to and it’s OK to be open with her.’ (S6PW3).

Participants in all sites described differences between the culture of clinical services in the host trust and the ethos underpinning peer support:

‘…it’s about the values because what I find with the other types of support, it all tends to be clinical and deficits based … very directive and judgemental … some of the clinical teams are stuck in that way of seeing things, that deficit-based thing and they don’t really know too much about peer support.’ (S5PW1).

At all sites, there was a perceived lack of contact with, and feedback from, community mental health teams, sometimes accompanied by a lack of understanding of the PW role:

‘Whenever I got a new service user, I’d email their [Community Psychiatric Nurse] or care coordinator … to give them more information about it and nobody, apart from I think one person, got back to me. So that’s been quite challenging, not really having any communication or contact really with the mental health teams that are working with the service users …’ (S5PW3).

Interviewees in all sites remarked that the timing of the offer of peer support - prior to discharge from hospital - was particularly challenging for some, especially in relation to maintaining contact with the PW following discharge. This represented a barrier to engagement that was related to the clinical context, rather than implementation:

‘… they are being introduced to it as soon as they come out … they are going through a tough period of fear, of not knowing what’s next for them. The last thing they want is to commit to 16 weeks of meeting someone that they don’t even know.’ (S2PW2). ‘I suspect that the post-discharge needs more targeting, that would be my sense. There are people who really get so much out of it, but then there are an awful lot who just disengage. It’s another stress for them I think.’ (S4PWC).

Implementation in high fidelity-high engagement cases

There was evidence of features supporting implementation in the high fidelity-engagement cases which contrasted with low fidelity-lowengagement cases (see below). In high fidelity cases, cultural differences between clinical services and peer support were generally seen as an asset and were valued, rather than as a source of tension:

‘… you need a values-based practice and how important it is, as opposed to the clinical based practice and how helpful that is … I’m not saying the clinical approach is wrong or anything like that, what I’m saying is we need to complement each other, we need to take a holistic approach.’ (S5PW1).

Some aspects of organisational culture were seen as supportive of peer support, including the role of recovery colleges in preparing PWs for the role or providing additional training once in post (recovery colleges employ an adult education model to supporting people with their mental health, often co-delivered by people using mental health services [ 34 ]):

‘… we were in a really fortunate position being linked with a Recovery College, that, where later in their work they then wanted to do specific recovery focused training around diagnosis we were able to provide that for people.’ (S3PWC).

In these cases, staff on the wards (inpatient units) were reported as largely familiar with and valuing the role of peer support:

‘… when I’d go on the ward … they seemed to see great value in the transparency of people being there because they’ve got lived experience. That aspect of it was really nice … good for the culture of the organisation in many ways.’ (S5PWC). ‘… the clinical teams are aware … they’re very excited that we’ve got peer workers on the ward. They’re very positive about it.’ (S3PW3).

PWCs described PW recruitment as having followed the process specified in the intervention handbook, and as such the PWs who were appointed were well equipped to deliver the role:

‘… we had the right people to execute these roles effectively really … we had quite a diverse selection panel … we had the right people that expressed the interest I think …’ (S5PWC).

There was evidence that PWs and PWCs – as intervention facilitators - had worked hard in delivering clinical team preparation sessions, as specified in the handbook, offering repeat sessions where necessary, and that this had supported a good relationship with ward teams:

‘… [in] the early days we went in to talk about ENRICH and then if they’d had significant staff turnover, which is really happening a lot … we’d then go back to the teams just so that they were aware of what ENRICH was about, what their role was … it certainly meant that staff were much more welcoming of the ENRICH peer workers when they came onto the wards.’ (S3PWC).

PWCs reported being well resourced in their leadership role, both in terms of having sufficient time to do the work and having sufficient supervision themselves around any difficult issues that might arise:

‘… [my role] was two days a week and that was plenty of time…’ (S3PWC). ‘I have had unconditional support from my manager … it’s been part of my regular monthly supervision … any kind of difficulties I’ve had or frustrations or whatever that has come up, that has been an ideal time to go through it. But I’ve also been supported to discuss things as and when they come up …’ (S5PWC).

In these sites, there was evidence that delivery of peer support was highly consistent with the manual. There was notable emphasis on flexible application of peer support, especially around pacing support in response to the individual’s needs, spending as much time as necessary alongside the participant to build a trusting relationship:

‘… it doesn’t necessarily follow a linear path a lot of the time. Sometimes, somebody might be having a really bad week and they actually want you to listen to what’s been going on for them … at the beginning, because you are getting to know the person as well, I think the kind of conversation you’d have is a bit more general … and then it might actually take a completely different path however many meetings down the line and they’ll actually go … “I haven’t told anyone about a particular issue, but I want to talk it through with you and see what you think”.’ (S3PW1).

PWs at these sites demonstrated confidence in taking a lead from the person they were supporting, consistent with the principles of choice and control that underpinned the intervention:

‘… I’m kind of getting to know things that they’re interested in and this is influencing where I signpost them to … it’s just about giving them the option and then they can make their own decision then whether they want to go, and again that’s putting them back in control, which is all about helping people to recover really and take control back of their lives.’ (S5PW2).

PWs also described learning from the people they were supporting, and the importance of validating their experiences, consistent with the principle of reciprocity in the underpinning framework:

‘There are people who I’m supporting who … realise that the medication is very important to them and that they will probably always be on it. So, I gain insight from that, just because maybe I found that medication in my own lived experience wasn’t particularly fantastic but for others it’s very important. So, you learn from other things … you’ve got to validate their experience because … they know what works for them and you can’t tell somebody else what will work for them …’ (S5PW1).

Implementation in low fidelity-low engagement cases

There was evidence of barriers to implementation in low fidelity-lowengagement cases. In both, PWs were employed in not-for-profit organisations, resulting in organisational context-related barriers to implementation. Resource issues impacted leadership of the intervention with, in one site, the organisation not having capacity to provide cover or suitable supervision for the PWC:

‘… we’ve had different staff line managing me over the past year because of maternity. But to be fair none of them really knew about ENRICH … there was nobody who could have covered my role here … it’s felt like a bit of pressure to continue doing it because I took a bit of time off … I couldn’t physically go out and do anything when I wasn’t well …’ (S6PWC).

Support for PWCs at these sites, including an Action Learning Set with other PWCs, was difficult to access because of lack of sufficient funding to travel to meetings:

‘I think the action learning sets worked really well … maybe they should have been planned for a bit more financially … because ultimately we had to go back to our Trust and say we need to find more money or I’m not going.’ (S4PWC).

Being outside of the NHS also created issues of access and authority for PWCs:

‘I would have thought there should be regular team meetings, but we never seemed to be able to get in on them … an additional disadvantage from being an organisation outside of the Trust …’ (S4PWC). ‘… it’s been difficult with the [NHS Trust], some of the staff there … I don’t want to say too much, but that’s been difficult.’ (S6PWC).

This extended to PWs being able to communicate with clinical teams about the people using:

‘A few times they didn’t want to talk to me because I didn’t have enough information for them … to establish who I was … I just wanted to know whether they were seeing [participant] or whether they’d stopped seeing him, and they wouldn’t tell me.’ (S4PW3).

At these sites there was, generally, a challenging relationship with ward-based clinical staff, potentially impacting on the initial relationship building phase of the peer support:

‘There were certainly, on that site, a lot of suspicious looks and “what on earth is this all about” type conversations. However much we tried to prepare the staff team, and we’d gone in and visited and talked to them all, but there was still that “what’s this all about”? People didn’t get it straight off.’ (S4PWC).

Cultural differences with the host NHS Trust were keenly felt by PWs employed in not-for-profit organisations:

‘… the ward environment is, well obviously it’s clinical. It sometimes feels some staff, but not all staff, who work on the wards are not really sure what my role is or have a vague understanding. There’s perhaps a little bit of a difference in terms of pecking order and me in the pecking order.’ (S6PW2). ‘… they will be looking at the patient’s files … they can build up a judgement before seeing you … when the patient sees the peer support worker they might talk to us because we’re non-judgemental, we don’t feedback unless there is a safeguarding issue or danger to themselves or others … I don’t think peers should be seeing files …’ (S4PW44).

Both sites also combined rural localities with urban areas, with issues of geography hindering timely delivery of peer support at remote hospital sites:

‘… the geography issue was a great challenge in itself in our area because I was one bit of the triangle and the [hospitals] were in two different places … I’d have had an hour or so travelling and then get there and “oh, they’re on leave until 10pm tonight”.’ (S4PWC).

Geography could also impact on building a strong sense of PW team:

‘I did lots of talking to [the PWC] but not so much my fellow peers. There was one fellow peer that I talk quite a lot to … the other two were very close to each other and so they were almost functioning as one … I got on OK with the people at [the other town] … it’s just that we had differences of opinion.’ (S4PW3).

There was some inconsistent delivery of training, with one PW reporting having received a truncated version of the training programme as a result of capacity issues:

‘I didn’t actually do [the full training] … because I was covering a maternity leave it was the girl did all the training. So, I basically had a morning with the coordinator where we went through the whole bumph together … ’ (S6PW3).

While the importance of group supervision was acknowledged in these sites, there was disruption leading to inconsistency with the pattern of weekly group supervision as a result geography in one site, and capacity in the other:

‘We don’t generally do weekly anymore … generally we do monthly although I check in by phone with them.’ (S4PWC). ‘… a lot of the supervision has ended up being one-to-one just because it’s a small team here … sometimes I would be able to meet with them together but often because my day, I’ve only got one a day week, I’d have to fit them in if one of them couldn’t do it that day …’ (S6PWC).

Possibly as a result of disruption to supervision or opportunities to support each other as a team, PWs at these sites at times appeared to lack confidence in delivering peer support:

‘… it made me feel that I was getting it all wrong … she didn’t really talk at all about, and I felt that I couldn’t, I just felt that I had to wait for her to give information to me … because that’s what I understood you are supposed to do, is wait for them to give you information to talk about their problems …’ (S4PW3). ‘… I’m imagining it’s going to be quite hard for a long time because the expression that I’ve used that comes to mind is pulling teeth. It’s going to be probably like that every time we meet … it is frustrating because you want to help them.’ (S6PW2).

Implementation in the outlier high fidelity-low engagement case

The outlier case shared contrasting sets of features with the other cases. Like high fidelity and engagement sites, the outlier case reported feedback from management describing a positive impact of peer support on culture in the NHS trust:

‘… within senior management they’ve seen the power of peer working and they really like it … we’re in discussions on when ENRICH finishes, that we’re going to have a number of peer workers within teams, exactly to try and change the nature and change the culture …’ (S2PWC).

PWs in this site also demonstrated a more confident, patient approach to relationship building:

‘… trying to build that friendly rapport, getting them to trust you, showing them that you understand them in a way … creating that safe space environment for them to be able to talk about how they are feeling or what’s going on for them … just finding out what they want to do for themselves not someone else telling them what to do … ’ (S2PW0).

However, as in the two low fidelity-low engagement cases, in the outlier site barriers to implementation included a challenging relationship with ward staff:

‘… [I feel] looked down upon sometimes, “oh, you’re just a peer support worker” … it’s the environment. The days that I do go for ward meetings are usually the days I need a long break, I’ll be honest with you …’ (S2PW2).

In this site there was also disruption to group supervision, with some PWs needing considerable additional support from the PWC and a challenging team dynamic emerging:

‘I was definitely doing weekly one-to-one supervisions with the peer workers when they first started … it kind of came apparent that it was what people needed … for me it didn’t work very well, I was exhausted … people want one-to-one sessions to talk about colleagues and issues they are having with their colleagues … I think there are two other peer workers who are less, they don’t see themselves as much as part of the team.’ (S2PWC).

The PWC indicated that they would have benefitted from additional support for their role:

‘I feel like we could have done more support around, more training kind of stuff on managing people with lived experience … … maybe one thing would have been more meetings with other peer worker coordinators and just see how other people are doing it … more guidance on what group supervision actually was … ’ (S2PWC).

This study used a qualitative, comparative case study design to explore how implementation of a peer support intervention might be associated with engagement with peer support and, as indicated in results elsewhere, [ 26 ] with outcomes. We noted clear differences related to organisational context between high fidelity-high engagement cases and low fidelity-low engagement cases. Lack of a positive working relationship between PW and ward (inpatient) clinical teams, exacerbated by lack of awareness of the potential role of peer support, is likely to be crucial to engagement where people begin peer support in hospital. Levels of engagement were highest in cases where those relationships were reported as largely positive and where differences in approach (between clinical practice and peer support) were highly valued [ 6 , 35 ].

We note that the two low fidelity-low engagement sites employed PWs in the not-for-profit sector rather than within the NHS. Elsewhere, research has indicated that the principles underpinning peer support might be better maintained within peer-led or not-for-profit organisations, [ 7 ] and that doing so might provide an opportunity to bring a change of culture into statutory services [ 35 ]. However, we observed constraints on resourcing for leadership roles, and lack of access and authority for managers in the not-for-profit sector, compounded, perhaps coincidentally, by the additional challenges of geography. Neither did we observe, in those sites, evidence of leadership for peer support from within the host NHS organisation that might have facilitated better implementation [ 36 ]. In our outlier high fidelity-low engagement case, resourcing for leadership also impacted support for PWs. Proper resourcing for PWCs has been identified elsewhere as crucial to providing good peer support [ 5 , 37 ]. PWCs at sites that struggled with levels of engagement identified the need for a wider network of mutual support beyond their immediate organisation, with work elsewhere highlighting the need to develop communities of practice around lived experience leadership roles in mental health services [ 38 , 39 ]. As such, our findings reinforce the link that has been observed elsewhere between leadership in implementation, and the outcomes of a newly implemented intervention [ 40 ].

At the two high engagement-high fidelity sites, PWCs noted that robust recruitment processes resulted in a PW team that were well equipped to deliver what was a challenging role. An experience of the PW team as mutually supportive, complemented with group supervision led by a PWC bringing experiential knowledge to their role, was identified as important at all five sites included in our analysis, as it is in the wider literature [ 2 , 5 ]. The PW training programme was equally valued across all sites with PWs indicating that it prepared them well for their roles. Again, the importance of training that is specifically tailored to peer support having been widely noted [ 3 , 4 ]. In sites where there were inconsistencies in delivery of supervision and training, this appeared to impact confidence among PWs in offering peer support that reflected the underpinning principles framework. Sites with high fidelity scores were indicative of a clear focus on relationship and trust building, characterised by spending time alongside the individual offered peer support, learning from them, before taking their lead in exploring new possibilities. These values have been identified as fundamental to peer support, [ 41 ] and our own analysis of data from the trial indicated that relationship building at the beginning of the peer support was predictive of ongoing engagement [ 42 ].

It is worth noting here that not all challenges to engaging people with the peer support were attributable to implementation issues. Across sites, interviewees felt that discharge from hospital was a challenging time for some people to consider taking up peer support. Other trials of peer support for discharge have also struggled in this respect, [ 43 ] especially where participants were those with a higher level of need (people with multiple admissions) as they were in our study [ 15 ].

Strengths and limitations

We employed a robust, theoretically informed comparative case study design, with case selection determined by a priori measures of fidelity [ 31 ] and engagement [ 26 ] made independently of this analysis. We analysed a complete data set – interviews of PWs and PWCs – in all sites included in the analysis, although we might usefully have also interviewed NHS clinicians and managers as they also played a role in implementation. Analysis of in-depth interviews exploring the experiences of people offered peer support will be reported elsewhere. Our original interview schedules were not directly informed by the PAHRIS framework [ 22 ] and so may not have elicited a full range of data relating to implementation variables. Other frameworks might have been indicative of different barriers and facilitators of successful implementation. Nevertheless, we note the work adapting the PAHRIS framework to elucidate the role of experiential knowledge in implementation was particularly suited to a study of peer support and informed by lived experience on the research team [ 25 ].

Implications for policy, practice and research

Mental health workforce policy in England, as elsewhere, is encouraging employment of large numbers of PWs into mental health services.[ 44 ]. A range of training programmes have emerged [ 45 ] that, to some degree, share a set of principles similar to those that informed ENRICH. This study suggests that specific supports for PWs need to be properly resourced as integral to the offer of peer support in mental health services. These include supervision from an experienced PW, opportunities for group supervision, and an emphasis on relationship building in PW training that is consistent with a principles-based peer support framework. While it has been suggested that peer support can drive cultural change in mental health provider organisations, [ 46 ] our research suggests that lack of supportive culture can constrain delivery. Peer leadership, provided with sufficient support and authority, is needed to support change work with clinical teams, in hospital and in the community, so that peer support and clinical care are part of a complementary offer.

This study identifies policy and practice implications when peers are employed through not-for-profit organisations to work in partnership with public mental health providers. Research elsewhere highlights the potential challenges and opportunities of this ‘hybrid’ approach, [ 35 , 47 ] indicating a need for strategies that effectively align implementation expectations between the not-for-profit organisation and the mental health provider.

Further research to develop and evaluate the introduction of peer support in mental health might usefully be informed by a change model that incorporates this range of implementation variables to optimise delivery of peer support. We also note that in our study, PWs were employed to, and supervised within a dedicated PW team that provided peer support across several clinical teams, while in many mental health services internationally PWs are employed as embedded members of multi-disciplinary clinical teams. There is a need for research that considers the implications for implementation and outcome of these contrasting organisational configurations.

This study provides clear indication that implementation issues can impact delivery of peer support, with implications for engagement and, potentially, outcomes. Resourcing can impact consistency of delivery, alongside challenges of access, authority and relationship with clinical teams, especially where PWs are employed outside of the mental health service. Attention needs to be paid to the impact of geography on implementation.

Data availability

The datasets used and analysed during the current study are available from the corresponding author on reasonable request.

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This study was funded by the UK National Institute for Health Research (NIHR), Programme Grants for Applied Research funding programme (grant number RP-PG-1212-20019). This paper presents independent research funded by NIHR. The views expressed are those of the authors and not necessarily those of the UK National Health Service (NHS), the NIHR or the Department of Health and Social Care.

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SG, SW, SLG, AlS, ML, JR, MR and JW contributed to the conception of the original study. SG, RF, SW, RB, PB, RE, DH, AlS and AnS contributed to the design of the work reported here. SG, RF, SW, RB, RE, AlS, ML, JR, MR and JW contributed to interpretation of the data. SG, RF, SW and JM contributed to the acquisition and analysis of data. SG, RF and SW drafted and substantively revised the work. All authors approved the submitted version of the study.

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Gillard, S., Foster, R., White, S. et al. Implementing peer support into practice in mental health services: a qualitative comparative case study. BMC Health Serv Res 24 , 1050 (2024). https://doi.org/10.1186/s12913-024-11447-5

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Methodology or method? A critical review of qualitative case study reports

Despite on-going debate about credibility, and reported limitations in comparison to other approaches, case study is an increasingly popular approach among qualitative researchers. We critically analysed the methodological descriptions of published case studies. Three high-impact qualitative methods journals were searched to locate case studies published in the past 5 years; 34 were selected for analysis. Articles were categorized as health and health services ( n= 12), social sciences and anthropology ( n= 7), or methods ( n= 15) case studies. The articles were reviewed using an adapted version of established criteria to determine whether adequate methodological justification was present, and if study aims, methods, and reported findings were consistent with a qualitative case study approach. Findings were grouped into five themes outlining key methodological issues: case study methodology or method, case of something particular and case selection, contextually bound case study, researcher and case interactions and triangulation, and study design inconsistent with methodology reported. Improved reporting of case studies by qualitative researchers will advance the methodology for the benefit of researchers and practitioners.

Case study research is an increasingly popular approach among qualitative researchers (Thomas, 2011 ). Several prominent authors have contributed to methodological developments, which has increased the popularity of case study approaches across disciplines (Creswell, 2013b ; Denzin & Lincoln, 2011b ; Merriam, 2009 ; Ragin & Becker, 1992 ; Stake, 1995 ; Yin, 2009 ). Current qualitative case study approaches are shaped by paradigm, study design, and selection of methods, and, as a result, case studies in the published literature vary. Differences between published case studies can make it difficult for researchers to define and understand case study as a methodology.

Experienced qualitative researchers have identified case study research as a stand-alone qualitative approach (Denzin & Lincoln, 2011b ). Case study research has a level of flexibility that is not readily offered by other qualitative approaches such as grounded theory or phenomenology. Case studies are designed to suit the case and research question and published case studies demonstrate wide diversity in study design. There are two popular case study approaches in qualitative research. The first, proposed by Stake ( 1995 ) and Merriam ( 2009 ), is situated in a social constructivist paradigm, whereas the second, by Yin ( 2012 ), Flyvbjerg ( 2011 ), and Eisenhardt ( 1989 ), approaches case study from a post-positivist viewpoint. Scholarship from both schools of inquiry has contributed to the popularity of case study and development of theoretical frameworks and principles that characterize the methodology.

The diversity of case studies reported in the published literature, and on-going debates about credibility and the use of case study in qualitative research practice, suggests that differences in perspectives on case study methodology may prevent researchers from developing a mutual understanding of practice and rigour. In addition, discussion about case study limitations has led some authors to query whether case study is indeed a methodology (Luck, Jackson, & Usher, 2006 ; Meyer, 2001 ; Thomas, 2010 ; Tight, 2010 ). Methodological discussion of qualitative case study research is timely, and a review is required to analyse and understand how this methodology is applied in the qualitative research literature. The aims of this study were to review methodological descriptions of published qualitative case studies, to review how the case study methodological approach was applied, and to identify issues that need to be addressed by researchers, editors, and reviewers. An outline of the current definitions of case study and an overview of the issues proposed in the qualitative methodological literature are provided to set the scene for the review.

Definitions of qualitative case study research

Case study research is an investigation and analysis of a single or collective case, intended to capture the complexity of the object of study (Stake, 1995 ). Qualitative case study research, as described by Stake ( 1995 ), draws together “naturalistic, holistic, ethnographic, phenomenological, and biographic research methods” in a bricoleur design, or in his words, “a palette of methods” (Stake, 1995 , pp. xi–xii). Case study methodology maintains deep connections to core values and intentions and is “particularistic, descriptive and heuristic” (Merriam, 2009 , p. 46).

As a study design, case study is defined by interest in individual cases rather than the methods of inquiry used. The selection of methods is informed by researcher and case intuition and makes use of naturally occurring sources of knowledge, such as people or observations of interactions that occur in the physical space (Stake, 1998 ). Thomas ( 2011 ) suggested that “analytical eclecticism” is a defining factor (p. 512). Multiple data collection and analysis methods are adopted to further develop and understand the case, shaped by context and emergent data (Stake, 1995 ). This qualitative approach “explores a real-life, contemporary bounded system (a case ) or multiple bounded systems (cases) over time, through detailed, in-depth data collection involving multiple sources of information … and reports a case description and case themes ” (Creswell, 2013b , p. 97). Case study research has been defined by the unit of analysis, the process of study, and the outcome or end product, all essentially the case (Merriam, 2009 ).

The case is an object to be studied for an identified reason that is peculiar or particular. Classification of the case and case selection procedures informs development of the study design and clarifies the research question. Stake ( 1995 ) proposed three types of cases and study design frameworks. These include the intrinsic case, the instrumental case, and the collective instrumental case. The intrinsic case is used to understand the particulars of a single case, rather than what it represents. An instrumental case study provides insight on an issue or is used to refine theory. The case is selected to advance understanding of the object of interest. A collective refers to an instrumental case which is studied as multiple, nested cases, observed in unison, parallel, or sequential order. More than one case can be simultaneously studied; however, each case study is a concentrated, single inquiry, studied holistically in its own entirety (Stake, 1995 , 1998 ).

Researchers who use case study are urged to seek out what is common and what is particular about the case. This involves careful and in-depth consideration of the nature of the case, historical background, physical setting, and other institutional and political contextual factors (Stake, 1998 ). An interpretive or social constructivist approach to qualitative case study research supports a transactional method of inquiry, where the researcher has a personal interaction with the case. The case is developed in a relationship between the researcher and informants, and presented to engage the reader, inviting them to join in this interaction and in case discovery (Stake, 1995 ). A postpositivist approach to case study involves developing a clear case study protocol with careful consideration of validity and potential bias, which might involve an exploratory or pilot phase, and ensures that all elements of the case are measured and adequately described (Yin, 2009 , 2012 ).

Current methodological issues in qualitative case study research

The future of qualitative research will be influenced and constructed by the way research is conducted, and by what is reviewed and published in academic journals (Morse, 2011 ). If case study research is to further develop as a principal qualitative methodological approach, and make a valued contribution to the field of qualitative inquiry, issues related to methodological credibility must be considered. Researchers are required to demonstrate rigour through adequate descriptions of methodological foundations. Case studies published without sufficient detail for the reader to understand the study design, and without rationale for key methodological decisions, may lead to research being interpreted as lacking in quality or credibility (Hallberg, 2013 ; Morse, 2011 ).

There is a level of artistic license that is embraced by qualitative researchers and distinguishes practice, which nurtures creativity, innovation, and reflexivity (Denzin & Lincoln, 2011b ; Morse, 2009 ). Qualitative research is “inherently multimethod” (Denzin & Lincoln, 2011a , p. 5); however, with this creative freedom, it is important for researchers to provide adequate description for methodological justification (Meyer, 2001 ). This includes paradigm and theoretical perspectives that have influenced study design. Without adequate description, study design might not be understood by the reader, and can appear to be dishonest or inaccurate. Reviewers and readers might be confused by the inconsistent or inappropriate terms used to describe case study research approach and methods, and be distracted from important study findings (Sandelowski, 2000 ). This issue extends beyond case study research, and others have noted inconsistencies in reporting of methodology and method by qualitative researchers. Sandelowski ( 2000 , 2010 ) argued for accurate identification of qualitative description as a research approach. She recommended that the selected methodology should be harmonious with the study design, and be reflected in methods and analysis techniques. Similarly, Webb and Kevern ( 2000 ) uncovered inconsistencies in qualitative nursing research with focus group methods, recommending that methodological procedures must cite seminal authors and be applied with respect to the selected theoretical framework. Incorrect labelling using case study might stem from the flexibility in case study design and non-directional character relative to other approaches (Rosenberg & Yates, 2007 ). Methodological integrity is required in design of qualitative studies, including case study, to ensure study rigour and to enhance credibility of the field (Morse, 2011 ).

Case study has been unnecessarily devalued by comparisons with statistical methods (Eisenhardt, 1989 ; Flyvbjerg, 2006 , 2011 ; Jensen & Rodgers, 2001 ; Piekkari, Welch, & Paavilainen, 2009 ; Tight, 2010 ; Yin, 1999 ). It is reputed to be the “the weak sibling” in comparison to other, more rigorous, approaches (Yin, 2009 , p. xiii). Case study is not an inherently comparative approach to research. The objective is not statistical research, and the aim is not to produce outcomes that are generalizable to all populations (Thomas, 2011 ). Comparisons between case study and statistical research do little to advance this qualitative approach, and fail to recognize its inherent value, which can be better understood from the interpretive or social constructionist viewpoint of other authors (Merriam, 2009 ; Stake, 1995 ). Building on discussions relating to “fuzzy” (Bassey, 2001 ), or naturalistic generalizations (Stake, 1978 ), or transference of concepts and theories (Ayres, Kavanaugh, & Knafl, 2003 ; Morse et al., 2011 ) would have more relevance.

Case study research has been used as a catch-all design to justify or add weight to fundamental qualitative descriptive studies that do not fit with other traditional frameworks (Merriam, 2009 ). A case study has been a “convenient label for our research—when we ‘can't think of anything ‘better”—in an attempt to give it [qualitative methodology] some added respectability” (Tight, 2010 , p. 337). Qualitative case study research is a pliable approach (Merriam, 2009 ; Meyer, 2001 ; Stake, 1995 ), and has been likened to a “curious methodological limbo” (Gerring, 2004 , p. 341) or “paradigmatic bridge” (Luck et al., 2006 , p. 104), that is on the borderline between postpositivist and constructionist interpretations. This has resulted in inconsistency in application, which indicates that flexibility comes with limitations (Meyer, 2001 ), and the open nature of case study research might be off-putting to novice researchers (Thomas, 2011 ). The development of a well-(in)formed theoretical framework to guide a case study should improve consistency, rigour, and trust in studies published in qualitative research journals (Meyer, 2001 ).

Assessment of rigour

The purpose of this study was to analyse the methodological descriptions of case studies published in qualitative methods journals. To do this we needed to develop a suitable framework, which used existing, established criteria for appraising qualitative case study research rigour (Creswell, 2013b ; Merriam, 2009 ; Stake, 1995 ). A number of qualitative authors have developed concepts and criteria that are used to determine whether a study is rigorous (Denzin & Lincoln, 2011b ; Lincoln, 1995 ; Sandelowski & Barroso, 2002 ). The criteria proposed by Stake ( 1995 ) provide a framework for readers and reviewers to make judgements regarding case study quality, and identify key characteristics essential for good methodological rigour. Although each of the factors listed in Stake's criteria could enhance the quality of a qualitative research report, in Table I we present an adapted criteria used in this study, which integrates more recent work by Merriam ( 2009 ) and Creswell ( 2013b ). Stake's ( 1995 ) original criteria were separated into two categories. The first list of general criteria is “relevant for all qualitative research.” The second list, “high relevance to qualitative case study research,” was the criteria that we decided had higher relevance to case study research. This second list was the main criteria used to assess the methodological descriptions of the case studies reviewed. The complete table has been preserved so that the reader can determine how the original criteria were adapted.

Framework for assessing quality in qualitative case study research.

Adapted from Stake ( 1995 , p. 131).

Study design

The critical review method described by Grant and Booth ( 2009 ) was used, which is appropriate for the assessment of research quality, and is used for literature analysis to inform research and practice. This type of review goes beyond the mapping and description of scoping or rapid reviews, to include “analysis and conceptual innovation” (Grant & Booth, 2009 , p. 93). A critical review is used to develop existing, or produce new, hypotheses or models. This is different to systematic reviews that answer clinical questions. It is used to evaluate existing research and competing ideas, to provide a “launch pad” for conceptual development and “subsequent testing” (Grant & Booth, 2009 , p. 93).

Qualitative methods journals were located by a search of the 2011 ISI Journal Citation Reports in Social Science, via the database Web of Knowledge (see m.webofknowledge.com). No “qualitative research methods” category existed in the citation reports; therefore, a search of all categories was performed using the term “qualitative.” In Table II , we present the qualitative methods journals located, ranked by impact factor. The highest ranked journals were selected for searching. We acknowledge that the impact factor ranking system might not be the best measure of journal quality (Cheek, Garnham, & Quan, 2006 ); however, this was the most appropriate and accessible method available.

International Journal of Qualitative Studies on Health and Well-being.

Search strategy

In March 2013, searches of the journals, Qualitative Health Research , Qualitative Research , and Qualitative Inquiry were completed to retrieve studies with “case study” in the abstract field. The search was limited to the past 5 years (1 January 2008 to 1 March 2013). The objective was to locate published qualitative case studies suitable for assessment using the adapted criterion. Viewpoints, commentaries, and other article types were excluded from review. Title and abstracts of the 45 retrieved articles were read by the first author, who identified 34 empirical case studies for review. All authors reviewed the 34 studies to confirm selection and categorization. In Table III , we present the 34 case studies grouped by journal, and categorized by research topic, including health sciences, social sciences and anthropology, and methods research. There was a discrepancy in categorization of one article on pedagogy and a new teaching method published in Qualitative Inquiry (Jorrín-Abellán, Rubia-Avi, Anguita-Martínez, Gómez-Sánchez, & Martínez-Mones, 2008 ). Consensus was to allocate to the methods category.

Outcomes of search of qualitative methods journals.

In Table III , the number of studies located, and final numbers selected for review have been reported. Qualitative Health Research published the most empirical case studies ( n= 16). In the health category, there were 12 case studies of health conditions, health services, and health policy issues, all published in Qualitative Health Research . Seven case studies were categorized as social sciences and anthropology research, which combined case study with biography and ethnography methodologies. All three journals published case studies on methods research to illustrate a data collection or analysis technique, methodological procedure, or related issue.

The methodological descriptions of 34 case studies were critically reviewed using the adapted criteria. All articles reviewed contained a description of study methods; however, the length, amount of detail, and position of the description in the article varied. Few studies provided an accurate description and rationale for using a qualitative case study approach. In the 34 case studies reviewed, three described a theoretical framework informed by Stake ( 1995 ), two by Yin ( 2009 ), and three provided a mixed framework informed by various authors, which might have included both Yin and Stake. Few studies described their case study design, or included a rationale that explained why they excluded or added further procedures, and whether this was to enhance the study design, or to better suit the research question. In 26 of the studies no reference was provided to principal case study authors. From reviewing the description of methods, few authors provided a description or justification of case study methodology that demonstrated how their study was informed by the methodological literature that exists on this approach.

The methodological descriptions of each study were reviewed using the adapted criteria, and the following issues were identified: case study methodology or method; case of something particular and case selection; contextually bound case study; researcher and case interactions and triangulation; and, study design inconsistent with methodology. An outline of how the issues were developed from the critical review is provided, followed by a discussion of how these relate to the current methodological literature.

Case study methodology or method

A third of the case studies reviewed appeared to use a case report method, not case study methodology as described by principal authors (Creswell, 2013b ; Merriam, 2009 ; Stake, 1995 ; Yin, 2009 ). Case studies were identified as a case report because of missing methodological detail and by review of the study aims and purpose. These reports presented data for small samples of no more than three people, places or phenomenon. Four studies, or “case reports” were single cases selected retrospectively from larger studies (Bronken, Kirkevold, Martinsen, & Kvigne, 2012 ; Coltart & Henwood, 2012 ; Hooghe, Neimeyer, & Rober, 2012 ; Roscigno et al., 2012 ). Case reports were not a case of something, instead were a case demonstration or an example presented in a report. These reports presented outcomes, and reported on how the case could be generalized. Descriptions focussed on the phenomena, rather than the case itself, and did not appear to study the case in its entirety.

Case reports had minimal in-text references to case study methodology, and were informed by other qualitative traditions or secondary sources (Adamson & Holloway, 2012 ; Buzzanell & D'Enbeau, 2009 ; Nagar-Ron & Motzafi-Haller, 2011 ). This does not suggest that case study methodology cannot be multimethod, however, methodology should be consistent in design, be clearly described (Meyer, 2001 ; Stake, 1995 ), and maintain focus on the case (Creswell, 2013b ).

To demonstrate how case reports were identified, three examples are provided. The first, Yeh ( 2013 ) described their study as, “the examination of the emergence of vegetarianism in Victorian England serves as a case study to reveal the relationships between boundaries and entities” (p. 306). The findings were a historical case report, which resulted from an ethnographic study of vegetarianism. Cunsolo Willox, Harper, Edge, ‘My Word’: Storytelling and Digital Media Lab, and Rigolet Inuit Community Government (2013) used “a case study that illustrates the usage of digital storytelling within an Inuit community” (p. 130). This case study reported how digital storytelling can be used with indigenous communities as a participatory method to illuminate the benefits of this method for other studies. This “case study was conducted in the Inuit community” but did not include the Inuit community in case analysis (Cunsolo Willox et al., 2013 , p. 130). Bronken et al. ( 2012 ) provided a single case report to demonstrate issues observed in a larger clinical study of aphasia and stroke, without adequate case description or analysis.

Case study of something particular and case selection

Case selection is a precursor to case analysis, which needs to be presented as a convincing argument (Merriam, 2009 ). Descriptions of the case were often not adequate to ascertain why the case was selected, or whether it was a particular exemplar or outlier (Thomas, 2011 ). In a number of case studies in the health and social science categories, it was not explicit whether the case was of something particular, or peculiar to their discipline or field (Adamson & Holloway, 2012 ; Bronken et al., 2012 ; Colón-Emeric et al., 2010 ; Jackson, Botelho, Welch, Joseph, & Tennstedt, 2012 ; Mawn et al., 2010 ; Snyder-Young, 2011 ). There were exceptions in the methods category ( Table III ), where cases were selected by researchers to report on a new or innovative method. The cases emerged through heuristic study, and were reported to be particular, relative to the existing methods literature (Ajodhia-Andrews & Berman, 2009 ; Buckley & Waring, 2013 ; Cunsolo Willox et al., 2013 ; De Haene, Grietens, & Verschueren, 2010 ; Gratton & O'Donnell, 2011 ; Sumsion, 2013 ; Wimpenny & Savin-Baden, 2012 ).

Case selection processes were sometimes insufficient to understand why the case was selected from the global population of cases, or what study of this case would contribute to knowledge as compared with other possible cases (Adamson & Holloway, 2012 ; Bronken et al., 2012 ; Colón-Emeric et al., 2010 ; Jackson et al., 2012 ; Mawn et al., 2010 ). In two studies, local cases were selected (Barone, 2010 ; Fourie & Theron, 2012 ) because the researcher was familiar with and had access to the case. Possible limitations of a convenience sample were not acknowledged. Purposeful sampling was used to recruit participants within the case of one study, but not of the case itself (Gallagher et al., 2013 ). Random sampling was completed for case selection in two studies (Colón-Emeric et al., 2010 ; Jackson et al., 2012 ), which has limited meaning in interpretive qualitative research.

To demonstrate how researchers provided a good justification for the selection of case study approaches, four examples are provided. The first, cases of residential care homes, were selected because of reported occurrences of mistreatment, which included residents being locked in rooms at night (Rytterström, Unosson, & Arman, 2013 ). Roscigno et al. ( 2012 ) selected cases of parents who were admitted for early hospitalization in neonatal intensive care with a threatened preterm delivery before 26 weeks. Hooghe et al. ( 2012 ) used random sampling to select 20 couples that had experienced the death of a child; however, the case study was of one couple and a particular metaphor described only by them. The final example, Coltart and Henwood ( 2012 ), provided a detailed account of how they selected two cases from a sample of 46 fathers based on personal characteristics and beliefs. They described how the analysis of the two cases would contribute to their larger study on first time fathers and parenting.

Contextually bound case study

The limits or boundaries of the case are a defining factor of case study methodology (Merriam, 2009 ; Ragin & Becker, 1992 ; Stake, 1995 ; Yin, 2009 ). Adequate contextual description is required to understand the setting or context in which the case is revealed. In the health category, case studies were used to illustrate a clinical phenomenon or issue such as compliance and health behaviour (Colón-Emeric et al., 2010 ; D'Enbeau, Buzzanell, & Duckworth, 2010 ; Gallagher et al., 2013 ; Hooghe et al., 2012 ; Jackson et al., 2012 ; Roscigno et al., 2012 ). In these case studies, contextual boundaries, such as physical and institutional descriptions, were not sufficient to understand the case as a holistic system, for example, the general practitioner (GP) clinic in Gallagher et al. ( 2013 ), or the nursing home in Colón-Emeric et al. ( 2010 ). Similarly, in the social science and methods categories, attention was paid to some components of the case context, but not others, missing important information required to understand the case as a holistic system (Alexander, Moreira, & Kumar, 2012 ; Buzzanell & D'Enbeau, 2009 ; Nairn & Panelli, 2009 ; Wimpenny & Savin-Baden, 2012 ).

In two studies, vicarious experience or vignettes (Nairn & Panelli, 2009 ) and images (Jorrín-Abellán et al., 2008 ) were effective to support description of context, and might have been a useful addition for other case studies. Missing contextual boundaries suggests that the case might not be adequately defined. Additional information, such as the physical, institutional, political, and community context, would improve understanding of the case (Stake, 1998 ). In Boxes 1 and 2 , we present brief synopses of two studies that were reviewed, which demonstrated a well bounded case. In Box 1 , Ledderer ( 2011 ) used a qualitative case study design informed by Stake's tradition. In Box 2 , Gillard, Witt, and Watts ( 2011 ) were informed by Yin's tradition. By providing a brief outline of the case studies in Boxes 1 and 2 , we demonstrate how effective case boundaries can be constructed and reported, which may be of particular interest to prospective case study researchers.

Article synopsis of case study research using Stake's tradition

Ledderer ( 2011 ) used a qualitative case study research design, informed by modern ethnography. The study is bounded to 10 general practice clinics in Denmark, who had received federal funding to implement preventative care services based on a Motivational Interviewing intervention. The researcher question focussed on “why is it so difficult to create change in medical practice?” (Ledderer, 2011 , p. 27). The study context was adequately described, providing detail on the general practitioner (GP) clinics and relevant political and economic influences. Methodological decisions are described in first person narrative, providing insight on researcher perspectives and interaction with the case. Forty-four interviews were conducted, which focussed on how GPs conducted consultations, and the form, nature and content, rather than asking their opinion or experience (Ledderer, 2011 , p. 30). The duration and intensity of researcher immersion in the case enhanced depth of description and trustworthiness of study findings. Analysis was consistent with Stake's tradition, and the researcher provided examples of inquiry techniques used to challenge assumptions about emerging themes. Several other seminal qualitative works were cited. The themes and typology constructed are rich in narrative data and storytelling by clinic staff, demonstrating individual clinic experiences as well as shared meanings and understandings about changing from a biomedical to psychological approach to preventative health intervention. Conclusions make note of social and cultural meanings and lessons learned, which might not have been uncovered using a different methodology.

Article synopsis of case study research using Yin's tradition

Gillard et al. ( 2011 ) study of camps for adolescents living with HIV/AIDs provided a good example of Yin's interpretive case study approach. The context of the case is bounded by the three summer camps of which the researchers had prior professional involvement. A case study protocol was developed that used multiple methods to gather information at three data collection points coinciding with three youth camps (Teen Forum, Discover Camp, and Camp Strong). Gillard and colleagues followed Yin's ( 2009 ) principles, using a consistent data protocol that enhanced cross-case analysis. Data described the young people, the camp physical environment, camp schedule, objectives and outcomes, and the staff of three youth camps. The findings provided a detailed description of the context, with less detail of individual participants, including insight into researcher's interpretations and methodological decisions throughout the data collection and analysis process. Findings provided the reader with a sense of “being there,” and are discovered through constant comparison of the case with the research issues; the case is the unit of analysis. There is evidence of researcher immersion in the case, and Gillard reports spending significant time in the field in a naturalistic and integrated youth mentor role.

This case study is not intended to have a significant impact on broader health policy, although does have implications for health professionals working with adolescents. Study conclusions will inform future camps for young people with chronic disease, and practitioners are able to compare similarities between this case and their own practice (for knowledge translation). No limitations of this article were reported. Limitations related to publication of this case study were that it was 20 pages long and used three tables to provide sufficient description of the camp and program components, and relationships with the research issue.

Researcher and case interactions and triangulation

Researcher and case interactions and transactions are a defining feature of case study methodology (Stake, 1995 ). Narrative stories, vignettes, and thick description are used to provoke vicarious experience and a sense of being there with the researcher in their interaction with the case. Few of the case studies reviewed provided details of the researcher's relationship with the case, researcher–case interactions, and how these influenced the development of the case study (Buzzanell & D'Enbeau, 2009 ; D'Enbeau et al., 2010 ; Gallagher et al., 2013 ; Gillard et al., 2011 ; Ledderer, 2011 ; Nagar-Ron & Motzafi-Haller, 2011 ). The role and position of the researcher needed to be self-examined and understood by readers, to understand how this influenced interactions with participants, and to determine what triangulation is needed (Merriam, 2009 ; Stake, 1995 ).

Gillard et al. ( 2011 ) provided a good example of triangulation, comparing data sources in a table (p. 1513). Triangulation of sources was used to reveal as much depth as possible in the study by Nagar-Ron and Motzafi-Haller ( 2011 ), while also enhancing confirmation validity. There were several case studies that would have benefited from improved range and use of data sources, and descriptions of researcher–case interactions (Ajodhia-Andrews & Berman, 2009 ; Bronken et al., 2012 ; Fincham, Scourfield, & Langer, 2008 ; Fourie & Theron, 2012 ; Hooghe et al., 2012 ; Snyder-Young, 2011 ; Yeh, 2013 ).

Study design inconsistent with methodology

Good, rigorous case studies require a strong methodological justification (Meyer, 2001 ) and a logical and coherent argument that defines paradigm, methodological position, and selection of study methods (Denzin & Lincoln, 2011b ). Methodological justification was insufficient in several of the studies reviewed (Barone, 2010 ; Bronken et al., 2012 ; Hooghe et al., 2012 ; Mawn et al., 2010 ; Roscigno et al., 2012 ; Yeh, 2013 ). This was judged by the absence, or inadequate or inconsistent reference to case study methodology in-text.

In six studies, the methodological justification provided did not relate to case study. There were common issues identified. Secondary sources were used as primary methodological references indicating that study design might not have been theoretically sound (Colón-Emeric et al., 2010 ; Coltart & Henwood, 2012 ; Roscigno et al., 2012 ; Snyder-Young, 2011 ). Authors and sources cited in methodological descriptions were inconsistent with the actual study design and practices used (Fourie & Theron, 2012 ; Hooghe et al., 2012 ; Jorrín-Abellán et al., 2008 ; Mawn et al., 2010 ; Rytterström et al., 2013 ; Wimpenny & Savin-Baden, 2012 ). This occurred when researchers cited Stake or Yin, or both (Mawn et al., 2010 ; Rytterström et al., 2013 ), although did not follow their paradigmatic or methodological approach. In 26 studies there were no citations for a case study methodological approach.

The findings of this study have highlighted a number of issues for researchers. A considerable number of case studies reviewed were missing key elements that define qualitative case study methodology and the tradition cited. A significant number of studies did not provide a clear methodological description or justification relevant to case study. Case studies in health and social sciences did not provide sufficient information for the reader to understand case selection, and why this case was chosen above others. The context of the cases were not described in adequate detail to understand all relevant elements of the case context, which indicated that cases may have not been contextually bounded. There were inconsistencies between reported methodology, study design, and paradigmatic approach in case studies reviewed, which made it difficult to understand the study methodology and theoretical foundations. These issues have implications for methodological integrity and honesty when reporting study design, which are values of the qualitative research tradition and are ethical requirements (Wager & Kleinert, 2010a ). Poorly described methodological descriptions may lead the reader to misinterpret or discredit study findings, which limits the impact of the study, and, as a collective, hinders advancements in the broader qualitative research field.

The issues highlighted in our review build on current debates in the case study literature, and queries about the value of this methodology. Case study research can be situated within different paradigms or designed with an array of methods. In order to maintain the creativity and flexibility that is valued in this methodology, clearer descriptions of paradigm and theoretical position and methods should be provided so that study findings are not undervalued or discredited. Case study research is an interdisciplinary practice, which means that clear methodological descriptions might be more important for this approach than other methodologies that are predominantly driven by fewer disciplines (Creswell, 2013b ).

Authors frequently omit elements of methodologies and include others to strengthen study design, and we do not propose a rigid or purist ideology in this paper. On the contrary, we encourage new ideas about using case study, together with adequate reporting, which will advance the value and practice of case study. The implications of unclear methodological descriptions in the studies reviewed were that study design appeared to be inconsistent with reported methodology, and key elements required for making judgements of rigour were missing. It was not clear whether the deviations from methodological tradition were made by researchers to strengthen the study design, or because of misinterpretations. Morse ( 2011 ) recommended that innovations and deviations from practice are best made by experienced researchers, and that a novice might be unaware of the issues involved with making these changes. To perpetuate the tradition of case study research, applications in the published literature should have consistencies with traditional methodological constructions, and deviations should be described with a rationale that is inherent in study conduct and findings. Providing methodological descriptions that demonstrate a strong theoretical foundation and coherent study design will add credibility to the study, while ensuring the intrinsic meaning of case study is maintained.

The value of this review is that it contributes to discussion of whether case study is a methodology or method. We propose possible reasons why researchers might make this misinterpretation. Researchers may interchange the terms methods and methodology, and conduct research without adequate attention to epistemology and historical tradition (Carter & Little, 2007 ; Sandelowski, 2010 ). If the rich meaning that naming a qualitative methodology brings to the study is not recognized, a case study might appear to be inconsistent with the traditional approaches described by principal authors (Creswell, 2013a ; Merriam, 2009 ; Stake, 1995 ; Yin, 2009 ). If case studies are not methodologically and theoretically situated, then they might appear to be a case report.

Case reports are promoted by university and medical journals as a method of reporting on medical or scientific cases; guidelines for case reports are publicly available on websites ( http://www.hopkinsmedicine.org/institutional_review_board/guidelines_policies/guidelines/case_report.html ). The various case report guidelines provide a general criteria for case reports, which describes that this form of report does not meet the criteria of research, is used for retrospective analysis of up to three clinical cases, and is primarily illustrative and for educational purposes. Case reports can be published in academic journals, but do not require approval from a human research ethics committee. Traditionally, case reports describe a single case, to explain how and what occurred in a selected setting, for example, to illustrate a new phenomenon that has emerged from a larger study. A case report is not necessarily particular or the study of a case in its entirety, and the larger study would usually be guided by a different research methodology.

This description of a case report is similar to what was provided in some studies reviewed. This form of report lacks methodological grounding and qualities of research rigour. The case report has publication value in demonstrating an example and for dissemination of knowledge (Flanagan, 1999 ). However, case reports have different meaning and purpose to case study, which needs to be distinguished. Findings of our review suggest that the medical understanding of a case report has been confused with qualitative case study approaches.

In this review, a number of case studies did not have methodological descriptions that included key characteristics of case study listed in the adapted criteria, and several issues have been discussed. There have been calls for improvements in publication quality of qualitative research (Morse, 2011 ), and for improvements in peer review of submitted manuscripts (Carter & Little, 2007 ; Jasper, Vaismoradi, Bondas, & Turunen, 2013 ). The challenging nature of editor and reviewers responsibilities are acknowledged in the literature (Hames, 2013 ; Wager & Kleinert, 2010b ); however, review of case study methodology should be prioritized because of disputes on methodological value.

Authors using case study approaches are recommended to describe their theoretical framework and methods clearly, and to seek and follow specialist methodological advice when needed (Wager & Kleinert, 2010a ). Adequate page space for case study description would contribute to better publications (Gillard et al., 2011 ). Capitalizing on the ability to publish complementary resources should be considered.

Limitations of the review

There is a level of subjectivity involved in this type of review and this should be considered when interpreting study findings. Qualitative methods journals were selected because the aims and scope of these journals are to publish studies that contribute to methodological discussion and development of qualitative research. Generalist health and social science journals were excluded that might have contained good quality case studies. Journals in business or education were also excluded, although a review of case studies in international business journals has been published elsewhere (Piekkari et al., 2009 ).

The criteria used to assess the quality of the case studies were a set of qualitative indicators. A numerical or ranking system might have resulted in different results. Stake's ( 1995 ) criteria have been referenced elsewhere, and was deemed the best available (Creswell, 2013b ; Crowe et al., 2011 ). Not all qualitative studies are reported in a consistent way and some authors choose to report findings in a narrative form in comparison to a typical biomedical report style (Sandelowski & Barroso, 2002 ), if misinterpretations were made this may have affected the review.

Case study research is an increasingly popular approach among qualitative researchers, which provides methodological flexibility through the incorporation of different paradigmatic positions, study designs, and methods. However, whereas flexibility can be an advantage, a myriad of different interpretations has resulted in critics questioning the use of case study as a methodology. Using an adaptation of established criteria, we aimed to identify and assess the methodological descriptions of case studies in high impact, qualitative methods journals. Few articles were identified that applied qualitative case study approaches as described by experts in case study design. There were inconsistencies in methodology and study design, which indicated that researchers were confused whether case study was a methodology or a method. Commonly, there appeared to be confusion between case studies and case reports. Without clear understanding and application of the principles and key elements of case study methodology, there is a risk that the flexibility of the approach will result in haphazard reporting, and will limit its global application as a valuable, theoretically supported methodology that can be rigorously applied across disciplines and fields.

Conflict of interest and funding

The authors have not received any funding or benefits from industry or elsewhere to conduct this study.

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Implementing peer support into practice in mental health services: a qualitative comparative case study

• Department of Nursing
• Centre for Applied Research in Health
• School of Human and Health Sciences

Research output : Contribution to journal › Article › peer-review

BACKGROUND: Peer workers are people with personal experience of mental distress, employed within mental health services to support others with similar experiences. Research has identified a range of factors that might facilitate or hinder the introduction of new peer worker roles into mental health services. While there is mixed evidence for the effectiveness of peer worker delivered interventions, there are no studies exploring how implementation might be associated with effect.

METHODS: This was a qualitative comparative case study using data from interviews with 20 peer workers and their five supervisors. Peer workers delivered peer support for discharge from inpatient to community mental health care as part of a randomised controlled trial. In the trial, level of participant engagement with peer support was associated with better outcome (hospital readmission). Study sites with higher levels of engagement also had higher scores on a measure of fidelity to peer support principles. We compared data from sites with contrasting levels of engagement and fidelity using an analytical framework derived from implementation theory.

RESULTS: In high engagement-high fidelity sites, there was regular work with clinical teams preparing for working alongside peer workers, and a positive relationship between staff on inpatient wards and peer workers. The supervisor role was well resourced, and delivery of peer support was highly consistent with the intervention manual. In low engagement-low fidelity sites peer workers were employed in not-for-profit organisations to support people using public mental health services and in rural areas. Supervisors faced constrained resources and experienced barriers to joint working between organisations. In these sites, peer workers could experience challenging relationships with ward staff. Issues of geography and capacity limited opportunities for supervision and team-building, impacting consistency of delivery.

CONCLUSIONS: This study provides clear indication that implementation can impact delivery of peer support, with implications for engagement and, potentially, outcomes of peer worker interventions. Resourcing issues can have knock-on effects on consistency of delivery, alongside challenges of access, authority and relationship with clinical teams, especially where peer workers were employed in not-for-profit organisations. Attention needs to be paid to the impact of geography on implementation.

TRIAL REGISTRATION: ISRCTN registry number ISRCTN10043328, registered 28 November 2016.

This output contributes to the following UN Sustainable Development Goals (SDGs)

Access to Document

• 10.1186/s12913-024-11447-5 Licence: CC BY

Implementing peer support into practice in mental health services : a qualitative comparative case study. / Gillard, Steve; Foster, Rhiannon; White, Sarah et al.

T1 - Implementing peer support into practice in mental health services

T2 - a qualitative comparative case study

AU - Gillard, Steve

AU - Foster, Rhiannon

AU - White, Sarah

AU - Bhattacharya, Rahul

AU - Binfield, Paul

AU - Eborall, Rachel

AU - Gibson, Sarah L

AU - Harnett, Daniella

AU - Simpson, Alan

AU - Lucock, Mike

AU - Marks, Jacqueline

AU - Repper, Julie

AU - Rinaldi, Miles

AU - Salla, Anthony

AU - Worner, Jessica

N1 - © 2024. The Author(s).

PY - 2024/9/11

Y1 - 2024/9/11

N2 - BACKGROUND: Peer workers are people with personal experience of mental distress, employed within mental health services to support others with similar experiences. Research has identified a range of factors that might facilitate or hinder the introduction of new peer worker roles into mental health services. While there is mixed evidence for the effectiveness of peer worker delivered interventions, there are no studies exploring how implementation might be associated with effect.METHODS: This was a qualitative comparative case study using data from interviews with 20 peer workers and their five supervisors. Peer workers delivered peer support for discharge from inpatient to community mental health care as part of a randomised controlled trial. In the trial, level of participant engagement with peer support was associated with better outcome (hospital readmission). Study sites with higher levels of engagement also had higher scores on a measure of fidelity to peer support principles. We compared data from sites with contrasting levels of engagement and fidelity using an analytical framework derived from implementation theory.RESULTS: In high engagement-high fidelity sites, there was regular work with clinical teams preparing for working alongside peer workers, and a positive relationship between staff on inpatient wards and peer workers. The supervisor role was well resourced, and delivery of peer support was highly consistent with the intervention manual. In low engagement-low fidelity sites peer workers were employed in not-for-profit organisations to support people using public mental health services and in rural areas. Supervisors faced constrained resources and experienced barriers to joint working between organisations. In these sites, peer workers could experience challenging relationships with ward staff. Issues of geography and capacity limited opportunities for supervision and team-building, impacting consistency of delivery.CONCLUSIONS: This study provides clear indication that implementation can impact delivery of peer support, with implications for engagement and, potentially, outcomes of peer worker interventions. Resourcing issues can have knock-on effects on consistency of delivery, alongside challenges of access, authority and relationship with clinical teams, especially where peer workers were employed in not-for-profit organisations. Attention needs to be paid to the impact of geography on implementation.TRIAL REGISTRATION: ISRCTN registry number ISRCTN10043328, registered 28 November 2016.

AB - BACKGROUND: Peer workers are people with personal experience of mental distress, employed within mental health services to support others with similar experiences. Research has identified a range of factors that might facilitate or hinder the introduction of new peer worker roles into mental health services. While there is mixed evidence for the effectiveness of peer worker delivered interventions, there are no studies exploring how implementation might be associated with effect.METHODS: This was a qualitative comparative case study using data from interviews with 20 peer workers and their five supervisors. Peer workers delivered peer support for discharge from inpatient to community mental health care as part of a randomised controlled trial. In the trial, level of participant engagement with peer support was associated with better outcome (hospital readmission). Study sites with higher levels of engagement also had higher scores on a measure of fidelity to peer support principles. We compared data from sites with contrasting levels of engagement and fidelity using an analytical framework derived from implementation theory.RESULTS: In high engagement-high fidelity sites, there was regular work with clinical teams preparing for working alongside peer workers, and a positive relationship between staff on inpatient wards and peer workers. The supervisor role was well resourced, and delivery of peer support was highly consistent with the intervention manual. In low engagement-low fidelity sites peer workers were employed in not-for-profit organisations to support people using public mental health services and in rural areas. Supervisors faced constrained resources and experienced barriers to joint working between organisations. In these sites, peer workers could experience challenging relationships with ward staff. Issues of geography and capacity limited opportunities for supervision and team-building, impacting consistency of delivery.CONCLUSIONS: This study provides clear indication that implementation can impact delivery of peer support, with implications for engagement and, potentially, outcomes of peer worker interventions. Resourcing issues can have knock-on effects on consistency of delivery, alongside challenges of access, authority and relationship with clinical teams, especially where peer workers were employed in not-for-profit organisations. Attention needs to be paid to the impact of geography on implementation.TRIAL REGISTRATION: ISRCTN registry number ISRCTN10043328, registered 28 November 2016.

KW - Humans

KW - Peer Group

KW - Qualitative Research

KW - Mental Health Services/organization & administration

KW - Female

KW - Social Support

KW - Interviews as Topic

KW - Mental Disorders/therapy

KW - Middle Aged

U2 - 10.1186/s12913-024-11447-5

DO - 10.1186/s12913-024-11447-5

M3 - Article

C2 - 39261915

JO - BMC Health Services Research

JF - BMC Health Services Research

SN - 1472-6963

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College students with adhd: a selective review of qualitative studies.

1. Introduction

1.1. qualitative research methods, 1.2. the present study, 2. materials and methods, 2.1. search strategy, 2.2. study selection, 2.3. variable identification, 3.1. quantitative results, 3.2. qualitative results, 3.2.1. the college experience of students with adhd, 3.2.2. interventions, 3.2.3. cognitive and academic functioning, 3.2.4. self-functioning, 4. discussion, 5. conclusions, author contributions, conflicts of interest, appendix a. summaries of included studies, appendix a.1. the college experience of students with adhd, appendix a.1.1. college transitions, appendix a.1.2. adhd as an identity, appendix a.1.3. race, appendix a.1.4. community college, appendix a.2. interventions, appendix a.2.1. coaching, appendix a.2.2. strategies, appendix a.2.3. medication, appendix a.3. cognitive and academic functioning, appendix a.4. self-functioning.

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Cohen, S.L.; Shavel, K.; Lovett, B.J. College Students with ADHD: A Selective Review of Qualitative Studies. Disabilities 2024 , 4 , 658-677. https://doi.org/10.3390/disabilities4030041

Cohen SL, Shavel K, Lovett BJ. College Students with ADHD: A Selective Review of Qualitative Studies. Disabilities . 2024; 4(3):658-677. https://doi.org/10.3390/disabilities4030041

Cohen, Shira L., Katie Shavel, and Benjamin J. Lovett. 2024. "College Students with ADHD: A Selective Review of Qualitative Studies" Disabilities 4, no. 3: 658-677. https://doi.org/10.3390/disabilities4030041

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case selection and the comparative method: introducing the case selector

• Published: 14 August 2017
• Volume 17 , pages 422–436, ( 2018 )

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• brian r. urlacher 1  

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We introduce a web application, the Case Selector ( http://und.edu/faculty/brian.urlacher ), that facilitates comparative case study research designs by creating an exhaustive comparison of cases from a dataset on the dependent, independent, and control variables specified by the user. This application was created to aid in systematic and transparent case selection so that researchers can better address the charge that cases are ‘cherry picked.’ An examination of case selection in a prominent study of rebel behaviour in civil war is then used to illustrate different applications of the Case Selector.

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Acknowledgements

The authors would like to thank the anonymous reviewers for their insightful comments and feedback over the course of the review processes. This project has been significantly improved by their suggestions. The authors have also agreed to provide access to the Case Selector through their faculty webpages at their affiliated institutions.

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prescott, t., urlacher, b.r. case selection and the comparative method: introducing the case selector. Eur Polit Sci 17 , 422–436 (2018). https://doi.org/10.1057/s41304-017-0128-5

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• Published: 19 September 2024

What do suicide loss survivors think of physician-assisted suicide: a comparative analysis of suicide loss survivors and the general population in Germany

• Laura Hofmann 1 ,
• Louisa Spieß 1 &
• Birgit Wagner 1  

BMC Medical Ethics volume  25 , Article number:  98 ( 2024 ) Cite this article

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Physician-assisted suicide (PAS) and voluntary euthanasia remain highly debated topics in society, drawing attention due to their ethical, legal, and emotional complexities. Within this debate, the loss of a loved one through suicide may shape the attitudes of survivors, resulting in more or less favorable attitudes towards this topic.

This study aims to explore and compare the attitudes towards PAS and voluntary euthanasia in a population of suicide loss survivors and the general population, while also considering socio-demographic factors.

A total of 529 participants, 168 of whom were survivors of suicide loss, completed an online questionnaire on their attitudes (NOBAS) and opinions (open response format) towards PAS and voluntary euthanasia, as well as regarding their legalization in Germany. The analysis consisted of both quantitative and qualitative components.

The entire sample showed positive attitudes towards PAS and voluntary euthanasia in terminally ill persons. Participants were more divided in their attitudes towards PAS in the case of a mental health disorder. Individuals without experienced suicide loss were more liberal regarding legalization in Germany and were more likely to understand the wish for PAS. Survivors of suicide loss were mainly concerned about the consequences for relatives. However, differences between both groups are small.

The experience of a loss by suicide influences attitudes towards PAS and voluntary euthanasia. Both groups showed an accepting attitude towards PAS and voluntary euthanasia, but also expressed concerns and fears regarding easy accessibility and consequences for grieving relatives.

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Introduction

Physician-assisted suicide (PAS) is now legal in an ever-increasing number of countries, bringing this topic to the focus of social and legal debates. PAS is defined as providing medication with the intention that it will result in the patient’s death [ 1 ]. The patient must take this medication independently, in contrast to voluntary euthanasia, where the doctor is authorized to administer the lethal medication. Physician-assisted suicide has been permitted in Germany since the decision of the Federal Constitutional Court in February 2020. Doctors and right-to-die organizations are permitted to provide PAS, however, there are ongoing debates about a new regulation. PAS is currently permitted for all individuals who meet certain requirements. These include, for example, that the individual must be capable of making an informed, free, and conscious decision. However, it is expected that there will be stricter regulations for PAS in the future. Voluntary euthanasia, on the other hand, remains prohibited in Germany.

In recent decades, the discourse surrounding end-of-life choices has become increasingly complex, marked by ethical, moral, and societal considerations. In Germany, the term (physician-) assisted suicide is still predominantly used, while the term assisted dying is increasingly used internationally as a collective term for both PAS and voluntary euthanasia [ 2 ].

Opinions differ widely on PAS and voluntary euthanasia. While some see these methods as long-needed options for self-determination, others see the danger of them becoming too easily accessible [ 2 ]. Recent studies have focused on attitudes towards PAS and voluntary euthanasia in the general population while also considering socio-demographic factors [ 3 , 4 , 5 ]. For example, a Norwegian study with 3.050 general population participants showed positive attitudes towards the legalization of PAS and voluntary euthanasia for patients with terminal illnesses, but participants were more critical towards PAS for people with mental health disorders or people without illnesses who are tired of life [ 4 ]. Younger and non-religious participants were more liberal towards PAS. A recent review from [ 2 ], consisting of 21 studies, found that younger age, higher education, higher socio-economic status, and lower religiosity are the most stable predictors of a liberal attitude towards PAS and voluntary euthanasia. Religious beliefs particularly seem to be an integral component of attitudes towards assisted dying. In a study from Belgium, the authors focused exclusively on the attitudes of the Muslim community towards PAS and voluntary euthanasia [ 3 ]. Their results indicated a clear rejection of both PAS and voluntary euthanasia, regardless of age and level of education. In a study from New Zealand, individuals from the general population also showed a largely positive attitude towards the topic [ 5 ]. The authors found no effect of age, but a moderate effect of religious belief. These studies have already provided insight into the public’s attitudes towards PAS and voluntary euthanasia and show that these attitudes are characterized by various socio-demographic factors in some countries or communities.

Other studies on this topic have focused more intensively on the attitudes of doctors and nursing staff who may be involved in preparing and providing assisted dying services [ 6 , 7 , 8 , 9 ]. In some studies, rather ambivalent attitudes towards PAS and voluntary euthanasia could be found across medical populations [ 10 ]. As doctors are the individuals responsible for providing medical aid in dying, their perspective is not only about legalization per se, but also about their role in the process and the potential conflict that arises against the background of also wishing to cure the patient. In a study from Norway [ 11 ], where PAS and voluntary euthanasia are currently not permitted, doctors were generally more opposed to legalization.

So far, most studies focus primarily on the attitudes of the general population and the associated legislation, as well as on medical staff, such as doctors and nurses [ 4 , 11 , 12 ]. However, perspectives shaped by a person’s own lived experience of suicide bereavement are still missing. Therefore, there is still little knowledge if this experience makes individuals more or less liberal in their perception of legalization of PAS. There are several reasons why suicide loss survivors might take a more liberal stance regarding assisted dying. A suicide is a violent and sudden death, which often has long-term and far-reaching consequences for the bereaved [ 13 , 14 , 15 ]. In particular, the idea of how the person might have died by suicide (e.g., railway suicides, jumping from high buildings) or even finding the person post-suicide can be highly distressing experiences, leaving the bereaved with long-term negative mental imageries [ 16 ]. Therefore, bereaved individuals might perceive PAS as a more peaceful and less violent way to end one's life. Assisted dying also offers the opportunity to say goodbye and accompany the person in their final days. This is something that relatives are unable to do after a suicide and which many experience as immensely difficult to process [ 17 ]. The wish for PAS is sometimes communicated by relatives and is less associated with feelings of guilt and responsibility for the death of loved ones [ 18 ]. Based on this experience, surviving relatives might take a more liberal view of the legalization of PAS and voluntary euthanasia after a suicide, as they might consider the loss through these methods to be less stressful than a loss through suicide.

However, the suicide bereaved might also show a less liberal attitude towards PAS. Survivors have experienced what it is like to lose a loved one first-hand and are aware of the impact it can have on the bereaved [ 19 ]. In some cases, the deceased person may have suffered from a mental health disorder and relatives may be concerned that people with mental health disorders will have access to PAS too quickly. They may also have experienced that the desire for suicide can fluctuate and is sometimes not stable over time.

To the best of our knowledge, no study to date focuses specifically on the attitudes towards PAS within a population of survivors of suicide loss. The purpose of this article is to present and compare the attitudes and thoughts of both survivors of suicide and individuals who have not experienced a loss by suicide. More specifically, the study aims to investigate a) the attitudes of suicide loss survivors and the general population, b) if the two groups differ in terms of their attitudes, c) whether attitudes vary according to socio-demographic factors and d) which topics are considered relevant regarding PAS. In order to be able to categorize the attitudes of bereaved individuals, these are compared with the attitudes of individuals who have not experienced a loss through suicide.

Design and study population

The study followed a cross-sectional design wherein participants filled in an online questionnaire. Participants had to meet the following inclusion criteria for participation: (1) aged 18 years or older, (2) possessed sufficient knowledge of German, and (3) provided signed informed consent. We included individuals with and without suicide loss, in order to compare the attitudes of both groups towards PAS. Individuals were excluded if they lost someone through PAS. Recruitment primarily took place via social media (Facebook, X, Instagram), e-mail mailing lists of various universities and through the Association for the Suicide Bereaved in Germany (AGUS e.V.). The Ethics Committee of the Medical School Berlin approved the study on July 12, 2023, in compliance with the current version of the Declaration of Helsinki (reference number: MSB-2023/117).

Sample characteristics

A total of 2.047 people accessed the questionnaire, 562 of whom completed it. Of these, 170 were survivors of suicide loss, of which two were excluded due to loss through PAS. Of the 392 participants without a suicide loss, 26 also had to be excluded due to a loss through PAS. A further five participants were excluded due to missing data. This resulted in a total sample of N  = 529, which was comprised of n  = 361 individuals without and n  = 168 with loss by suicide. In both samples, most participants were female with 91.1% in the suicide loss survivor sample and 94.2% in the non-loss sample. The mean age was 46.79 ( SD  = 11.29) years and 43.80 ( SD  = 10.59) years, respectively. All sample characteristics can be seen in Table  1 . We did not find significant differences between the groups for the characteristics we collected.

Socio-demographic data

Relevant socio-demographic data of the participants were collected, as well as information on the suicide loss and the deceased person, if applicable.

Questionnaire on attitudes of the Norwegian Bioethics Attitude Survey (NOBAS)

To assess participants’ attitudes towards PAS and voluntary euthanasia, the questionnaire from the NOBAS was used [ 4 , 20 ]. The questionnaire consists of eight items that cover various aspects of legalization of PAS and voluntary euthanasia. Opinions are rated on a 5-point Likert Scale from 1 =  strongly disagree to 5 =  strongly agree. The analysis is only possible on a descriptive level. While the original questionnaire uses the term active aid in dying in most questions, we used the term assisted suicide, as this is the commonly used term in Germany. The questionnaire also provides a definition of PAS and voluntary euthanasia in the introduction.

Questionnaire on legalization of PAS in Germany

To assess the opinions regarding the legalization of PAS in Germany as well as the personal opinions of the participant, a further eight items were added (e.g., "I would make use of assisted suicide if I were suffering from a serious physical illness"). The items are also rated on a 5-point Likert Scale from 1 =  strongly disagree to 5 =  strongly agree. In addition, participants were asked to write down their thoughts and views on PAS in an open response format (“Please let us know your thoughts and opinions on assisted suicide here.”). The term assisted suicide was used for these items as well. The questionnaire was developed for this study and can be found in Table S1 in the Supplementary Material.

Statistical analyses

Analyses were carried out using SPSS Version 28 [ 21 ]. Means and standard deviations were calculated for continuous variables, frequencies, and descriptive statistics for categorical variables. T-tests were used to analyze differences in attitudes towards PAS between groups with and without suicide loss. Differences in opinions between different socio-demographic groups were analyzed with several MANOVAs. The qualitative data of the open response format was analyzed following a deductive-inductive approach [ 22 ]. The data was first prepared for analysis and codes we subsequently generated, which were then applied to the data. If existing codes did not appear suitable, new codes were generated and applied to the data again. This procedure was repeated until the entire data set had been coded. The coding was carried out with MAXQDA 2022 [ 23 ] by two independent researchers (LH, LS) in order to ensure reliability. Any discrepancies were discussed.

Attitudes on PAS and voluntary euthanasia (NOBAS  +  additional items)

Overall, all participants showed a positive attitude towards PAS (Q1) and voluntary euthanasia (Q2) for people with terminal illnesses and a predominantly positive attitude towards PAS for people with incurable chronic illnesses (Q3). Both groups of participants showed divided attitudes towards PAS for people with mental health disorders (Q4) and for people without any illness but who are tired of living (Q5). Both groups neither agreed nor disagreed with these statements. The participants also mostly approved of the legalization of PAS in Germany (Q9) and were less concerned about the financial enrichment of right-to-die organizations (Q10). Participants in both groups generally showed a high level of understanding regarding the wish for PAS (Q12) and did not tend to be concerned that those affected would choose PAS too quickly (Q13). Participants reported that they would also be more likely to make use of PAS themselves if they were suffering from a severe physical illness (Q11). However, participants in both groups were undecided about PAS in the case of an own mental health disorder (Q16). All results are shown in Table  2 .

Participants who had not experienced a loss by suicide had a significantly more liberal attitude towards the legalization of PAS in Germany than people who had experienced a suicide loss, t (265.32) = 2.78, p  = 0.006., with an effect of d  = 0.27. Individuals who had not been bereaved by suicide were also significantly more likely to understand why someone might choose PAS, t (237.04) = 2.30, p  = 0.022., with a small effect of d  = 0.23. Survivors of suicide loss were significantly less understanding of the general wish for PAS, t (218.76) = -2.88, p  = 0.004., with an effect of d  = 0.30. However, it should be noted that the effect is minimal and both groups have almost identical mean values. We could not find any differences between the groups regarding other attitudes towards PAS, such as PAS being allowed for individuals with a mental health disorder. All results are shown in Table 3 . 

Attitudes towards PAS and voluntary assisted dying and demographic factors

Firstly, we analyzed the differences in general attitudes (first five questions of NOBAS) between the age groups 18–29, 30–39, 40–49, 50–59, and 60 + years while controlling for suicide loss. Individuals in the oldest subgroup showed the most negative attitudes towards the legalization of voluntary euthanasia for terminally ill patients (see Table  4 ). There were no significant differences between the age groups for the other items. Further, the differences in attitudes among people with secondary, higher secondary, and higher education were analyzed, while controlling for suicide loss. People with the highest level of education showed a more negative attitude towards voluntary euthanasia than the other subgroups. We then analyzed the attitudes of participants of different religions. However, only individuals of no religious belief, Protestant, and Catholic were assessed, as the sample of other religions was too small for the analysis. Participants of Catholic belief showed significantly more negative attitudes towards the legalization of PAS and voluntary euthanasia for all five items. In contrast, those with no religious beliefs showed significantly more liberal attitudes. However, it should also be noted here that the differences in mean values are minimal and no strong differences were found between the groups.

Opinions on PAS: Qualitative findings

The open question asking participants for their opinion on PAS was not a mandatory question, so a total of n  = 239 participants completed the open response format. A total of four categories were identified: (1) autonomy and dignity, (2) impact on relatives and bereavement, (3) avoidance of violent deaths and suffering, and (4) PAS for mental health disorders and physical illness. All categories are described in more detail below, and it is also indicated whether the comment comes from a survivor of suicide loss (SL) or a person who has not lost someone to suicide (NSL). Not all participants completed the free text field, as this question was optional.

Autonomy and dignity

In total, n  = 62 people mentioned a person’s autonomy and right to make decisions regarding their own death. Many participants also stated their own desire to die in a self-determined way. Making decisions regarding one’s own death and not having to wait for it to occur naturally was viewed as allowing one to die with dignity.

“If a person is suffering so much, whether physically or mentally, then they should be able to decide whether they want to leave this world and also decide when.” (SL)

“In my opinion, being able to leave the world with dignity and autonomy is a human right.” (NSL)

However, many participants also emphasized the importance of ensuring that the wish is autonomous and stable, while highlighting the need for multiple consultations with doctors or right-to-die organizations to avoid spontaneous decisions for PAS. Although some participants emphasized the importance of autonomy, concerns that the wish could be expressed at short notice and that other treatment options would not be attempted first were also reported.

“I think PAS makes complete sense if it really is out of the question that the person wants to continue living. It should not be a spontaneous decision.” (SL)

“It may be chosen too quickly. Hopelessness and the desire to die are not always permanent; it is an illness. So where do you draw the line? “ (SL)

PAS can also be a way of preventing an undignified death associated with great pain. This also considers that palliative care sometimes reaches its limits and not everyone can be cared for as painlessly as possible at the end of life. Other participants reported concerns that palliative care services might not be used to their full extent.

“I work in a hospice, and in rare cases even palliative medicine reaches its limits, so I think everyone should be allowed to decide independently when a situation is no longer bearable.” (NSL)

“ However, I also think it is important to offer more palliative care and to expand it so that an assisted suicide does not have to be necessary and the only way out. I think consciously living through the dying phase can also be very important .” (NSL)

Some participants also stated that the option of PAS is associated with feelings of relief, in that one could make decisions regarding their own death, and limit suffering, in the event of an illness.

“If I have missed my own last chance, I find it comforting to know that I could get help when the palliative options have been exhausted.” (SL)

Impact on relatives and bereavement

The impact of PAS on relatives was mentioned almost exclusively by survivors of suicide loss. A total of n  = 32 survivors spoke about their own experience and what consequences PAS could have for those close to the deceased person.

“Suicide is the cruelest way to die and means incomprehensible suffering for relatives. Assisted dying opens the possibility of saying goodbye and may not leave relatives with so many unanswered questions and horror images.” (SL)

“I think because I know the pain of suicide too well, it is very difficult to think about the topic in a neutral way on an emotional level (…), but if someone around me would decide to do it I would absolutely reject it.” (SL)

The lack of an opportunity to say goodbye is usually perceived as highly distressing for the bereaved. PAS could give those affected the opportunity to say goodbye, prepare for the death, and talk things through. Several bereaved participants stated that this would have helped them in the grieving process, as they did not have the opportunity to say goodbye to the person after the suicide took place.

“It would be better if you could say goodbye and hug the person (…). Instead of dying in secret, in pain, and alone, relatives could hold the person’s hand and support them. I wish I could have spoken to my sister one last time.” (SL)

“I would have loved to have been able to say goodbye and hold her hand in the last few minutes.” (SL)

Participants stated that they would have liked to have accompanied their loved ones— to have been there— so that the person did not have to die alone. Many reported that the thought of the person dying while feeling lonely to be highly distressing. PAS could give relatives the opportunity to be there for the dying person.

“I am convinced that no one should leave the world alone. Everyone should be able to feel the comfort and security of a familiar person.” (SL)

“I think accompanying the person is very very important. For the person who is dying but also for the bereaved. I would have liked to hold my husband’s hand to show him that I am here and that he is not alone in this moment.” (SL)

After the loss, survivors of suicide loss are also often confronted with feelings of guilt and responsibility for the suicide. Questions regarding the reason behind the suicide are often also present. Participants stated that these grief symptoms might not occur in the event of a loss through PAS.

“The grief for my partner would certainly have been the same, but it would not have been accompanied by images of horror and feelings of guilt. That’s what makes grieving after suicide so difficult.” (SL)

However, some bereaved participants opposed the legalization of PAS due to their own experiences. These individuals view assisted dying critically, expressing the high burden it places on relatives.

“I can’t imagine PAS at all, I’ve lost two people to suicide in the last year, it’s hard as a relative.” (SL)

“A difficult topic from my point of view as a bereaved person whose life has changed so much after the suicides of my husband and my brother. The pain and helplessness within the family is so significant that I find it hard to have an opinion on that.” (SL)

Avoidance of violent deaths and suffering

Both bereaved individuals and those without a suicide loss considered PAS to be a less violent death than suicide, and could be associated with less pain for both the deceased person as well as the bereaved.

“I would have wished for a less agonizing death for him. He drove his car into a tree.” (SL)

“In my opinion, a death through PAS would have been more humane and dignified than the agonizing and slow death by poisoning that she chose.” (SL)

Dying by PAS could also mean a gentler death than through suicide and might not entail the risk of long-term suffering. Some survivors also mentioned that the deceased person was still in a coma after the suicide and that they found this to be an additionally stressful experience.

“My mother was in a coma for three weeks after her suicide in an intensive care unit. That was the worst time for her and us.” (SL)

“I would like to have this option instead of the agonizing alternatives, which also make it worse for the relatives, like slitting your wrist. It’s about dying with dignity and not through a painful and brutal suicide.” (NSL)

PAS for mental health disorders and physical illnesses

It became evident that even among the participants, regardless of whether they had experienced a suicide loss or not, there was disagreement regarding PAS in cases of mental health disorders. The responses of n  = 34 participants were related to this topic. While some individuals emphasized the relevance of self-determination, regardless of the presence of an underlying illness, others limited self-determination to only in the case of incurable physical illnesses.

“Even if it is very difficult, the possibility of assisted dying should depend on personal suffering and not on the type of illness or impairment.“ (SL)

Some participants supported the legalization of PAS, but only in the case of physical illnesses. Some were concerned that the wish to die in individuals with mental health disorders may not be stable and due to a temporary crisis, which could recede again with therapeutic support. Some also reported their own suicidal thoughts during mental crises and that they could not rationally decide whether they wanted to live or die at that time.

“In the case of mental health disorders, I find it somewhat difficult to decide. I find it hard to grasp whether you can really make the decision with a clear mind and full consciousness.” (SL)

“I find it particularly hard in the field of mental health, because there are many suicide attempts and people are very happy they did survive.” (NSL)

In terms of mental health disorders, participants tended to emphasize the need for rapid suicide prevention support services and an expansion of therapeutic support. Some suggested developing separate regulations for PAS and voluntary euthanasia for people with mental health disorders. These suggestions highlighted the need for individuals to receive therapeutic support for a certain period before PAS is made possible. Others recommended monitoring individuals to assess the stability of their wishes over time.

“I take a different view of mental health disorders, where treatment options should first and foremost be expanded. And, above all, no patient at risk of suicide should have to spend months looking for therapy.” (SL)

The aim of the study was to provide an overview of attitudes towards assisted dying in individuals with and without suicide loss and to analyze the differences between the two groups, while also considering relevant socio-demographic factors. While previous research has examined the attitudes towards PAS across various population groups, so far, the own experience of suicide loss has not yet been included as a research perspective.

Overall, participants showed a positive attitude towards physician-assisted suicide and voluntary euthanasia for people with a terminal illness and a positive attitude towards the legalization of PAS in Germany, regardless of their experience of suicide loss. Regarding access for people without a physical illness, participants were rather divided in their attitudes. These results are in line with studies on attitudes in the general population [ 4 , 24 ]. Participants could also understand why people make use of PAS and were less concerned that right-to-die organizations could profit from it. Only few small differences between people with and without loss by suicide experiences were found. Participants without loss by suicide experiences showed more liberal attitudes towards legalization in Germany and were more likely to understand the wish for assisted dying. Survivors of suicide loss showed significantly less understanding of the wish for PAS. However, the difference is minimal and only statistically and not clinically and ethically significant. It is possible that larger differences between groups could be found if the sample were bigger or other factors were considered.

It is therefore not possible to conclusively conclude whether attitudes towards PAS are shaped by one’s own experience of loss. Further research is urgently needed to shed more light on this topic. Loss by suicide is associated with severe grief symptoms in the bereaved [ 14 , 25 ], as well as feelings of guilt and questions regarding the reasons behind the suicide. The pain of loss can lead to the bereaved being less liberal towards PAS due to the known consequences of death, as they know first-hand how devastating it can be and what effects it has on relatives. This population group may also be less sympathetic to the decision of PAS, as they might not understand how a person could choose an unnatural death and leave their relatives behind. However, some participants who experienced a suicide loss gave the impression that they saw assisted suicide as an alternative to (non-assisted) suicide. It is possible that this assumption influences the attitude towards assisted suicide and that participants perceive it more positively. Even if the questionnaire did not imply this, some suicide bereaved participants may have perceived it as such, which could in turn shape their attitudes.

This point is also reflected in the qualitative results, in which participants were asked to share their opinions on PAS. Survivors of suicide loss were particularly concerned about the impact on relatives in the event of assisted dying. Precisely because they have experienced a suicide loss, as well as the associated grief, these participants found the decision for PAS difficult to imagine. However, bereaved participants also emphasized the opportunity to say goodbye to the dying person and to be involved in the dying process, which might have a positive impact on bereavement. In their systematic review, [ 18 ] found that, in most studies, relatives who lost someone through PAS showed similar or even lower levels of grief and psychopathological outcomes than those who lost someone through a natural death. Against this background, it seems particularly helpful for individuals to be involved in the end-of-life decision-making process and to be able to prepare for the death. In another study, Snijdewind et al. [ 1 ] interviewed individuals who lost a partner through suicide or through physician-assisted dying due to a mental health disorder. Participants who lost their partner through physician-assisted dying showed lower grief reactions. Reasons for this could be that partners were involved in the decision-making process, were able to say goodbye and knew that the deceased chose death of their own free will. However, Wagner and Maercker [ 26 ] found increased depression and PTSD symptoms in relatives who were themselves present when the person died. Accompanying the dying process can, therefore, also have a negative impact on the mental health of relatives. However, the most frequently mentioned aspect among all participants was autonomy, which is consistent with several other studies on attitudes towards PAS and voluntary euthanasia [ 5 , 6 , 27 ]. Regardless of any existing experience of loss, autonomy seemed to be the most prevalent variable among the participants.

Lastly, we also found some small differences between groups of different age, education, and religion in some items. Older participants and those with a higher level of education were less in favor of voluntary euthanasia. People with no religious beliefs showed the most liberal attitudes towards PAS and voluntary euthanasia. Here, we also found statistically significant differences, but no major differences between the groups can be seen when considering the mean values. Nevertheless, these results are in line with previous studies that looked at attitudes towards PAS in different socio-demographic subgroups [ 2 , 3 , 28 ].

To the best of our knowledge, this study is the first to analyze attitudes towards PAS and voluntary euthanasia while considering individual’s own experience of suicide loss. We have a sufficiently large and heterogeneous sample in terms of age, level of education, religious belief, and experience of loss. The qualitative data also allowed us to examine a broad range of opinions, although the results should be interpreted against the background of some limitations. Our sample consisted of over 90% female participants, which means that generalizability is limited. One reason could be that we have mainly recruited via our social media channels, where significantly more women follow us than men, possibly due to a greater interest in psychology and mental health. The results therefore largely reflect the opinions of women. The cross-sectional design also does not allow any inferences about causality. Although the measurement instruments were used in a previous study, these have not been validated and can only be analyzed at item level. Conducting multiple tests can elevate the risk of random significant results and increase the likelihood of false-positive results. Since our analysis was performed at item level, no correction was applied. However, a questionnaire with the possibility of calculating subscales would be recommended for further analyses. The study was also not preregistered. We also had a high dropout rate at the beginning of the questionnaire. Most individuals didn’t even start the questionnaire after reading the first page. Nonetheless, the dropout rate may lead to a selection bias and can influence the generalizability of our findings. Although the two groups did not differ significantly in the socio-demographic data that we collected, it cannot be excluded that they differed in terms of other factors. For example, we did not collect data on political orientation, ethnic or cultural background, which could have an influence on opinions on PAS.

Conclusions

This study provides the first important insights into the attitudes of survivors of suicide loss and the general public regarding the regulations on PAS and voluntary euthanasia in Germany. So far, little is known about how the general population in Germany sees the new legal situation regarding PAS and how one’s own experience of suicide loss shape their attitudes. While the present results provide an overview of possible concerns and fears of individuals regarding PAS and voluntary euthanasia, they also highlight how complex and multi-layered this topic can be. Future research should address this topic in more detail, exploring a broader range of aspects when surveying attitudes while also including individuals who lost someone through PAS.

Availability of data and materials

The data can be requested from the first author.

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Laura Hofmann, Louisa Spieß & Birgit Wagner

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LH and BW designed and developed the study and wrote the ethics proposal. LH conducted the study and prepared and analysed the data. LS analysed the qualitative data as the second rater. LH and BW drafted the manuscript.

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Hofmann, L., Spieß, L. & Wagner, B. What do suicide loss survivors think of physician-assisted suicide: a comparative analysis of suicide loss survivors and the general population in Germany. BMC Med Ethics 25 , 98 (2024). https://doi.org/10.1186/s12910-024-01099-9

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Received : 30 April 2024

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DOI : https://doi.org/10.1186/s12910-024-01099-9

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