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10.1 Overview of Single-Subject Research

Learning objectives.

• Explain what single-subject research is, including how it differs from other types of psychological research.
• Explain what case studies are, including some of their strengths and weaknesses.
• Explain who uses single-subject research and why.

What Is Single-Subject Research?

Single-subject research is a type of quantitative research that involves studying in detail the behavior of each of a small number of participants. Note that the term single-subject does not mean that only one participant is studied; it is more typical for there to be somewhere between two and 10 participants. (This is why single-subject research designs are sometimes called small- n designs, where n is the statistical symbol for the sample size.) Single-subject research can be contrasted with group research , which typically involves studying large numbers of participants and examining their behavior primarily in terms of group means, standard deviations, and so on. The majority of this book is devoted to understanding group research, which is the most common approach in psychology. But single-subject research is an important alternative, and it is the primary approach in some areas of psychology.

Before continuing, it is important to distinguish single-subject research from two other approaches, both of which involve studying in detail a small number of participants. One is qualitative research, which focuses on understanding people’s subjective experience by collecting relatively unstructured data (e.g., detailed interviews) and analyzing those data using narrative rather than quantitative techniques. Single-subject research, in contrast, focuses on understanding objective behavior through experimental manipulation and control, collecting highly structured data, and analyzing those data quantitatively.

It is also important to distinguish single-subject research from case studies. A case study is a detailed description of an individual, which can include both qualitative and quantitative analyses. (Case studies that include only qualitative analyses can be considered a type of qualitative research.) The history of psychology is filled with influential cases studies, such as Sigmund Freud’s description of “Anna O.” (see Note 10.5 “The Case of “Anna O.”” ) and John Watson and Rosalie Rayner’s description of Little Albert (Watson & Rayner, 1920), who learned to fear a white rat—along with other furry objects—when the researchers made a loud noise while he was playing with the rat. Case studies can be useful for suggesting new research questions and for illustrating general principles. They can also help researchers understand rare phenomena, such as the effects of damage to a specific part of the human brain. As a general rule, however, case studies cannot substitute for carefully designed group or single-subject research studies. One reason is that case studies usually do not allow researchers to determine whether specific events are causally related, or even related at all. For example, if a patient is described in a case study as having been sexually abused as a child and then as having developed an eating disorder as a teenager, there is no way to determine whether these two events had anything to do with each other. A second reason is that an individual case can always be unusual in some way and therefore be unrepresentative of people more generally. Thus case studies have serious problems with both internal and external validity.

The Case of “Anna O.”

Sigmund Freud used the case of a young woman he called “Anna O.” to illustrate many principles of his theory of psychoanalysis (Freud, 1961). (Her real name was Bertha Pappenheim, and she was an early feminist who went on to make important contributions to the field of social work.) Anna had come to Freud’s colleague Josef Breuer around 1880 with a variety of odd physical and psychological symptoms. One of them was that for several weeks she was unable to drink any fluids. According to Freud,

She would take up the glass of water that she longed for, but as soon as it touched her lips she would push it away like someone suffering from hydrophobia.…She lived only on fruit, such as melons, etc., so as to lessen her tormenting thirst (p. 9).

But according to Freud, a breakthrough came one day while Anna was under hypnosis.

[S]he grumbled about her English “lady-companion,” whom she did not care for, and went on to describe, with every sign of disgust, how she had once gone into this lady’s room and how her little dog—horrid creature!—had drunk out of a glass there. The patient had said nothing, as she had wanted to be polite. After giving further energetic expression to the anger she had held back, she asked for something to drink, drank a large quantity of water without any difficulty, and awoke from her hypnosis with the glass at her lips; and thereupon the disturbance vanished, never to return.

Freud’s interpretation was that Anna had repressed the memory of this incident along with the emotion that it triggered and that this was what had caused her inability to drink. Furthermore, her recollection of the incident, along with her expression of the emotion she had repressed, caused the symptom to go away.

As an illustration of Freud’s theory, the case study of Anna O. is quite effective. As evidence for the theory, however, it is essentially worthless. The description provides no way of knowing whether Anna had really repressed the memory of the dog drinking from the glass, whether this repression had caused her inability to drink, or whether recalling this “trauma” relieved the symptom. It is also unclear from this case study how typical or atypical Anna’s experience was.

Figure 10.2

“Anna O.” was the subject of a famous case study used by Freud to illustrate the principles of psychoanalysis.

Wikimedia Commons – public domain.

Assumptions of Single-Subject Research

Again, single-subject research involves studying a small number of participants and focusing intensively on the behavior of each one. But why take this approach instead of the group approach? There are several important assumptions underlying single-subject research, and it will help to consider them now.

First and foremost is the assumption that it is important to focus intensively on the behavior of individual participants. One reason for this is that group research can hide individual differences and generate results that do not represent the behavior of any individual. For example, a treatment that has a positive effect for half the people exposed to it but a negative effect for the other half would, on average, appear to have no effect at all. Single-subject research, however, would likely reveal these individual differences. A second reason to focus intensively on individuals is that sometimes it is the behavior of a particular individual that is primarily of interest. A school psychologist, for example, might be interested in changing the behavior of a particular disruptive student. Although previous published research (both single-subject and group research) is likely to provide some guidance on how to do this, conducting a study on this student would be more direct and probably more effective.

A second assumption of single-subject research is that it is important to discover causal relationships through the manipulation of an independent variable, the careful measurement of a dependent variable, and the control of extraneous variables. For this reason, single-subject research is often considered a type of experimental research with good internal validity. Recall, for example, that Hall and his colleagues measured their dependent variable (studying) many times—first under a no-treatment control condition, then under a treatment condition (positive teacher attention), and then again under the control condition. Because there was a clear increase in studying when the treatment was introduced, a decrease when it was removed, and an increase when it was reintroduced, there is little doubt that the treatment was the cause of the improvement.

A third assumption of single-subject research is that it is important to study strong and consistent effects that have biological or social importance. Applied researchers, in particular, are interested in treatments that have substantial effects on important behaviors and that can be implemented reliably in the real-world contexts in which they occur. This is sometimes referred to as social validity (Wolf, 1976). The study by Hall and his colleagues, for example, had good social validity because it showed strong and consistent effects of positive teacher attention on a behavior that is of obvious importance to teachers, parents, and students. Furthermore, the teachers found the treatment easy to implement, even in their often chaotic elementary school classrooms.

Who Uses Single-Subject Research?

Single-subject research has been around as long as the field of psychology itself. In the late 1800s, one of psychology’s founders, Wilhelm Wundt, studied sensation and consciousness by focusing intensively on each of a small number of research participants. Herman Ebbinghaus’s research on memory and Ivan Pavlov’s research on classical conditioning are other early examples, both of which are still described in almost every introductory psychology textbook.

In the middle of the 20th century, B. F. Skinner clarified many of the assumptions underlying single-subject research and refined many of its techniques (Skinner, 1938). He and other researchers then used it to describe how rewards, punishments, and other external factors affect behavior over time. This work was carried out primarily using nonhuman subjects—mostly rats and pigeons. This approach, which Skinner called the experimental analysis of behavior —remains an important subfield of psychology and continues to rely almost exclusively on single-subject research. For excellent examples of this work, look at any issue of the Journal of the Experimental Analysis of Behavior . By the 1960s, many researchers were interested in using this approach to conduct applied research primarily with humans—a subfield now called applied behavior analysis (Baer, Wolf, & Risley, 1968). Applied behavior analysis plays an especially important role in contemporary research on developmental disabilities, education, organizational behavior, and health, among many other areas. Excellent examples of this work (including the study by Hall and his colleagues) can be found in the Journal of Applied Behavior Analysis .

Although most contemporary single-subject research is conducted from the behavioral perspective, it can in principle be used to address questions framed in terms of any theoretical perspective. For example, a studying technique based on cognitive principles of learning and memory could be evaluated by testing it on individual high school students using the single-subject approach. The single-subject approach can also be used by clinicians who take any theoretical perspective—behavioral, cognitive, psychodynamic, or humanistic—to study processes of therapeutic change with individual clients and to document their clients’ improvement (Kazdin, 1982).

Key Takeaways

• Single-subject research—which involves testing a small number of participants and focusing intensively on the behavior of each individual—is an important alternative to group research in psychology.
• Single-subject studies must be distinguished from case studies, in which an individual case is described in detail. Case studies can be useful for generating new research questions, for studying rare phenomena, and for illustrating general principles. However, they cannot substitute for carefully controlled experimental or correlational studies because they are low in internal and external validity.
• Single-subject research has been around since the beginning of the field of psychology. Today it is most strongly associated with the behavioral theoretical perspective, but it can in principle be used to study behavior from any perspective.
• Practice: Find and read a published article in psychology that reports new single-subject research. (A good source of articles published in the Journal of Applied Behavior Analysis can be found at http://seab.envmed.rochester.edu/jaba/jabaMostPop-2011.html .) Write a short summary of the study.

Practice: Find and read a published case study in psychology. (Use case study as a key term in a PsycINFO search.) Then do the following:

• Describe one problem related to internal validity.
• Describe one problem related to external validity.
• Generate one hypothesis suggested by the case study that might be interesting to test in a systematic single-subject or group study.

Baer, D. M., Wolf, M. M., & Risley, T. R. (1968). Some current dimensions of applied behavior analysis. Journal of Applied Behavior Analysis , 1 , 91–97.

Freud, S. (1961). Five lectures on psycho-analysis . New York, NY: Norton.

Kazdin, A. E. (1982). Single-case research designs: Methods for clinical and applied settings . New York, NY: Oxford University Press.

Skinner, B. F. (1938). The behavior of organisms: An experimental analysis . New York, NY: Appleton-Century-Crofts.

Watson, J. B., & Rayner, R. (1920). Conditioned emotional reactions. Journal of Experimental Psychology , 3 , 1–14.

Wolf, M. (1976). Social validity: The case for subjective measurement or how applied behavior analysis is finding its heart. Journal of Applied Behavior Analysis, 11 , 203–214.

Research Methods in Psychology Copyright © 2016 by University of Minnesota is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

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• Case Study | Definition, Examples & Methods

Case Study | Definition, Examples & Methods

Published on 5 May 2022 by Shona McCombes . Revised on 30 January 2023.

A case study is a detailed study of a specific subject, such as a person, group, place, event, organisation, or phenomenon. Case studies are commonly used in social, educational, clinical, and business research.

A case study research design usually involves qualitative methods , but quantitative methods are sometimes also used. Case studies are good for describing , comparing, evaluating, and understanding different aspects of a research problem .

Table of contents

When to do a case study, step 1: select a case, step 2: build a theoretical framework, step 3: collect your data, step 4: describe and analyse the case.

A case study is an appropriate research design when you want to gain concrete, contextual, in-depth knowledge about a specific real-world subject. It allows you to explore the key characteristics, meanings, and implications of the case.

Case studies are often a good choice in a thesis or dissertation . They keep your project focused and manageable when you don’t have the time or resources to do large-scale research.

You might use just one complex case study where you explore a single subject in depth, or conduct multiple case studies to compare and illuminate different aspects of your research problem.

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Once you have developed your problem statement and research questions , you should be ready to choose the specific case that you want to focus on. A good case study should have the potential to:

• Provide new or unexpected insights into the subject
• Challenge or complicate existing assumptions and theories
• Propose practical courses of action to resolve a problem
• Open up new directions for future research

Unlike quantitative or experimental research, a strong case study does not require a random or representative sample. In fact, case studies often deliberately focus on unusual, neglected, or outlying cases which may shed new light on the research problem.

If you find yourself aiming to simultaneously investigate and solve an issue, consider conducting action research . As its name suggests, action research conducts research and takes action at the same time, and is highly iterative and flexible. 

However, you can also choose a more common or representative case to exemplify a particular category, experience, or phenomenon.

While case studies focus more on concrete details than general theories, they should usually have some connection with theory in the field. This way the case study is not just an isolated description, but is integrated into existing knowledge about the topic. It might aim to:

• Exemplify a theory by showing how it explains the case under investigation
• Expand on a theory by uncovering new concepts and ideas that need to be incorporated
• Challenge a theory by exploring an outlier case that doesn’t fit with established assumptions

To ensure that your analysis of the case has a solid academic grounding, you should conduct a literature review of sources related to the topic and develop a theoretical framework . This means identifying key concepts and theories to guide your analysis and interpretation.

There are many different research methods you can use to collect data on your subject. Case studies tend to focus on qualitative data using methods such as interviews, observations, and analysis of primary and secondary sources (e.g., newspaper articles, photographs, official records). Sometimes a case study will also collect quantitative data .

The aim is to gain as thorough an understanding as possible of the case and its context.

In writing up the case study, you need to bring together all the relevant aspects to give as complete a picture as possible of the subject.

How you report your findings depends on the type of research you are doing. Some case studies are structured like a standard scientific paper or thesis, with separate sections or chapters for the methods , results , and discussion .

Others are written in a more narrative style, aiming to explore the case from various angles and analyse its meanings and implications (for example, by using textual analysis or discourse analysis ).

In all cases, though, make sure to give contextual details about the case, connect it back to the literature and theory, and discuss how it fits into wider patterns or debates.

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The Advantages and Limitations of Single Case Study Analysis

As Andrew Bennett and Colin Elman have recently noted, qualitative research methods presently enjoy “an almost unprecedented popularity and vitality… in the international relations sub-field”, such that they are now “indisputably prominent, if not pre-eminent” (2010: 499). This is, they suggest, due in no small part to the considerable advantages that case study methods in particular have to offer in studying the “complex and relatively unstructured and infrequent phenomena that lie at the heart of the subfield” (Bennett and Elman, 2007: 171). Using selected examples from within the International Relations literature[1], this paper aims to provide a brief overview of the main principles and distinctive advantages and limitations of single case study analysis. Divided into three inter-related sections, the paper therefore begins by first identifying the underlying principles that serve to constitute the case study as a particular research strategy, noting the somewhat contested nature of the approach in ontological, epistemological, and methodological terms. The second part then looks to the principal single case study types and their associated advantages, including those from within the recent ‘third generation’ of qualitative International Relations (IR) research. The final section of the paper then discusses the most commonly articulated limitations of single case studies; while accepting their susceptibility to criticism, it is however suggested that such weaknesses are somewhat exaggerated. The paper concludes that single case study analysis has a great deal to offer as a means of both understanding and explaining contemporary international relations.

The term ‘case study’, John Gerring has suggested, is “a definitional morass… Evidently, researchers have many different things in mind when they talk about case study research” (2006a: 17). It is possible, however, to distil some of the more commonly-agreed principles. One of the most prominent advocates of case study research, Robert Yin (2009: 14) defines it as “an empirical enquiry that investigates a contemporary phenomenon in depth and within its real-life context, especially when the boundaries between phenomenon and context are not clearly evident”. What this definition usefully captures is that case studies are intended – unlike more superficial and generalising methods – to provide a level of detail and understanding, similar to the ethnographer Clifford Geertz’s (1973) notion of ‘thick description’, that allows for the thorough analysis of the complex and particularistic nature of distinct phenomena. Another frequently cited proponent of the approach, Robert Stake, notes that as a form of research the case study “is defined by interest in an individual case, not by the methods of inquiry used”, and that “the object of study is a specific, unique, bounded system” (2008: 443, 445). As such, three key points can be derived from this – respectively concerning issues of ontology, epistemology, and methodology – that are central to the principles of single case study research.

First, the vital notion of ‘boundedness’ when it comes to the particular unit of analysis means that defining principles should incorporate both the synchronic (spatial) and diachronic (temporal) elements of any so-called ‘case’. As Gerring puts it, a case study should be “an intensive study of a single unit… a spatially bounded phenomenon – e.g. a nation-state, revolution, political party, election, or person – observed at a single point in time or over some delimited period of time” (2004: 342). It is important to note, however, that – whereas Gerring refers to a single unit of analysis – it may be that attention also necessarily be given to particular sub-units. This points to the important difference between what Yin refers to as an ‘holistic’ case design, with a single unit of analysis, and an ’embedded’ case design with multiple units of analysis (Yin, 2009: 50-52). The former, for example, would examine only the overall nature of an international organization, whereas the latter would also look to specific departments, programmes, or policies etc.

Secondly, as Tim May notes of the case study approach, “even the most fervent advocates acknowledge that the term has entered into understandings with little specification or discussion of purpose and process” (2011: 220). One of the principal reasons for this, he argues, is the relationship between the use of case studies in social research and the differing epistemological traditions – positivist, interpretivist, and others – within which it has been utilised. Philosophy of science concerns are obviously a complex issue, and beyond the scope of much of this paper. That said, the issue of how it is that we know what we know – of whether or not a single independent reality exists of which we as researchers can seek to provide explanation – does lead us to an important distinction to be made between so-called idiographic and nomothetic case studies (Gerring, 2006b). The former refers to those which purport to explain only a single case, are concerned with particularisation, and hence are typically (although not exclusively) associated with more interpretivist approaches. The latter are those focused studies that reflect upon a larger population and are more concerned with generalisation, as is often so with more positivist approaches[2]. The importance of this distinction, and its relation to the advantages and limitations of single case study analysis, is returned to below.

Thirdly, in methodological terms, given that the case study has often been seen as more of an interpretivist and idiographic tool, it has also been associated with a distinctly qualitative approach (Bryman, 2009: 67-68). However, as Yin notes, case studies can – like all forms of social science research – be exploratory, descriptive, and/or explanatory in nature. It is “a common misconception”, he notes, “that the various research methods should be arrayed hierarchically… many social scientists still deeply believe that case studies are only appropriate for the exploratory phase of an investigation” (Yin, 2009: 6). If case studies can reliably perform any or all three of these roles – and given that their in-depth approach may also require multiple sources of data and the within-case triangulation of methods – then it becomes readily apparent that they should not be limited to only one research paradigm. Exploratory and descriptive studies usually tend toward the qualitative and inductive, whereas explanatory studies are more often quantitative and deductive (David and Sutton, 2011: 165-166). As such, the association of case study analysis with a qualitative approach is a “methodological affinity, not a definitional requirement” (Gerring, 2006a: 36). It is perhaps better to think of case studies as transparadigmatic; it is mistaken to assume single case study analysis to adhere exclusively to a qualitative methodology (or an interpretivist epistemology) even if it – or rather, practitioners of it – may be so inclined. By extension, this also implies that single case study analysis therefore remains an option for a multitude of IR theories and issue areas; it is how this can be put to researchers’ advantage that is the subject of the next section.

Having elucidated the defining principles of the single case study approach, the paper now turns to an overview of its main benefits. As noted above, a lack of consensus still exists within the wider social science literature on the principles and purposes – and by extension the advantages and limitations – of case study research. Given that this paper is directed towards the particular sub-field of International Relations, it suggests Bennett and Elman’s (2010) more discipline-specific understanding of contemporary case study methods as an analytical framework. It begins however, by discussing Harry Eckstein’s seminal (1975) contribution to the potential advantages of the case study approach within the wider social sciences.

Eckstein proposed a taxonomy which usefully identified what he considered to be the five most relevant types of case study. Firstly were so-called configurative-idiographic studies, distinctly interpretivist in orientation and predicated on the assumption that “one cannot attain prediction and control in the natural science sense, but only understanding ( verstehen )… subjective values and modes of cognition are crucial” (1975: 132). Eckstein’s own sceptical view was that any interpreter ‘simply’ considers a body of observations that are not self-explanatory and “without hard rules of interpretation, may discern in them any number of patterns that are more or less equally plausible” (1975: 134). Those of a more post-modernist bent, of course – sharing an “incredulity towards meta-narratives”, in Lyotard’s (1994: xxiv) evocative phrase – would instead suggest that this more free-form approach actually be advantageous in delving into the subtleties and particularities of individual cases.

Eckstein’s four other types of case study, meanwhile, promote a more nomothetic (and positivist) usage. As described, disciplined-configurative studies were essentially about the use of pre-existing general theories, with a case acting “passively, in the main, as a receptacle for putting theories to work” (Eckstein, 1975: 136). As opposed to the opportunity this presented primarily for theory application, Eckstein identified heuristic case studies as explicit theoretical stimulants – thus having instead the intended advantage of theory-building. So-called p lausibility probes entailed preliminary attempts to determine whether initial hypotheses should be considered sound enough to warrant more rigorous and extensive testing. Finally, and perhaps most notably, Eckstein then outlined the idea of crucial case studies , within which he also included the idea of ‘most-likely’ and ‘least-likely’ cases; the essential characteristic of crucial cases being their specific theory-testing function.

Whilst Eckstein’s was an early contribution to refining the case study approach, Yin’s (2009: 47-52) more recent delineation of possible single case designs similarly assigns them roles in the applying, testing, or building of theory, as well as in the study of unique cases[3]. As a subset of the latter, however, Jack Levy (2008) notes that the advantages of idiographic cases are actually twofold. Firstly, as inductive/descriptive cases – akin to Eckstein’s configurative-idiographic cases – whereby they are highly descriptive, lacking in an explicit theoretical framework and therefore taking the form of “total history”. Secondly, they can operate as theory-guided case studies, but ones that seek only to explain or interpret a single historical episode rather than generalise beyond the case. Not only does this therefore incorporate ‘single-outcome’ studies concerned with establishing causal inference (Gerring, 2006b), it also provides room for the more postmodern approaches within IR theory, such as discourse analysis, that may have developed a distinct methodology but do not seek traditional social scientific forms of explanation.

Applying specifically to the state of the field in contemporary IR, Bennett and Elman identify a ‘third generation’ of mainstream qualitative scholars – rooted in a pragmatic scientific realist epistemology and advocating a pluralistic approach to methodology – that have, over the last fifteen years, “revised or added to essentially every aspect of traditional case study research methods” (2010: 502). They identify ‘process tracing’ as having emerged from this as a central method of within-case analysis. As Bennett and Checkel observe, this carries the advantage of offering a methodologically rigorous “analysis of evidence on processes, sequences, and conjunctures of events within a case, for the purposes of either developing or testing hypotheses about causal mechanisms that might causally explain the case” (2012: 10).

Harnessing various methods, process tracing may entail the inductive use of evidence from within a case to develop explanatory hypotheses, and deductive examination of the observable implications of hypothesised causal mechanisms to test their explanatory capability[4]. It involves providing not only a coherent explanation of the key sequential steps in a hypothesised process, but also sensitivity to alternative explanations as well as potential biases in the available evidence (Bennett and Elman 2010: 503-504). John Owen (1994), for example, demonstrates the advantages of process tracing in analysing whether the causal factors underpinning democratic peace theory are – as liberalism suggests – not epiphenomenal, but variously normative, institutional, or some given combination of the two or other unexplained mechanism inherent to liberal states. Within-case process tracing has also been identified as advantageous in addressing the complexity of path-dependent explanations and critical junctures – as for example with the development of political regime types – and their constituent elements of causal possibility, contingency, closure, and constraint (Bennett and Elman, 2006b).

Bennett and Elman (2010: 505-506) also identify the advantages of single case studies that are implicitly comparative: deviant, most-likely, least-likely, and crucial cases. Of these, so-called deviant cases are those whose outcome does not fit with prior theoretical expectations or wider empirical patterns – again, the use of inductive process tracing has the advantage of potentially generating new hypotheses from these, either particular to that individual case or potentially generalisable to a broader population. A classic example here is that of post-independence India as an outlier to the standard modernisation theory of democratisation, which holds that higher levels of socio-economic development are typically required for the transition to, and consolidation of, democratic rule (Lipset, 1959; Diamond, 1992). Absent these factors, MacMillan’s single case study analysis (2008) suggests the particularistic importance of the British colonial heritage, the ideology and leadership of the Indian National Congress, and the size and heterogeneity of the federal state.

Most-likely cases, as per Eckstein above, are those in which a theory is to be considered likely to provide a good explanation if it is to have any application at all, whereas least-likely cases are ‘tough test’ ones in which the posited theory is unlikely to provide good explanation (Bennett and Elman, 2010: 505). Levy (2008) neatly refers to the inferential logic of the least-likely case as the ‘Sinatra inference’ – if a theory can make it here, it can make it anywhere. Conversely, if a theory cannot pass a most-likely case, it is seriously impugned. Single case analysis can therefore be valuable for the testing of theoretical propositions, provided that predictions are relatively precise and measurement error is low (Levy, 2008: 12-13). As Gerring rightly observes of this potential for falsification:

“a positivist orientation toward the work of social science militates toward a greater appreciation of the case study format, not a denigration of that format, as is usually supposed” (Gerring, 2007: 247, emphasis added).

In summary, the various forms of single case study analysis can – through the application of multiple qualitative and/or quantitative research methods – provide a nuanced, empirically-rich, holistic account of specific phenomena. This may be particularly appropriate for those phenomena that are simply less amenable to more superficial measures and tests (or indeed any substantive form of quantification) as well as those for which our reasons for understanding and/or explaining them are irreducibly subjective – as, for example, with many of the normative and ethical issues associated with the practice of international relations. From various epistemological and analytical standpoints, single case study analysis can incorporate both idiographic sui generis cases and, where the potential for generalisation may exist, nomothetic case studies suitable for the testing and building of causal hypotheses. Finally, it should not be ignored that a signal advantage of the case study – with particular relevance to international relations – also exists at a more practical rather than theoretical level. This is, as Eckstein noted, “that it is economical for all resources: money, manpower, time, effort… especially important, of course, if studies are inherently costly, as they are if units are complex collective individuals ” (1975: 149-150, emphasis added).

Limitations

Single case study analysis has, however, been subject to a number of criticisms, the most common of which concern the inter-related issues of methodological rigour, researcher subjectivity, and external validity. With regard to the first point, the prototypical view here is that of Zeev Maoz (2002: 164-165), who suggests that “the use of the case study absolves the author from any kind of methodological considerations. Case studies have become in many cases a synonym for freeform research where anything goes”. The absence of systematic procedures for case study research is something that Yin (2009: 14-15) sees as traditionally the greatest concern due to a relative absence of methodological guidelines. As the previous section suggests, this critique seems somewhat unfair; many contemporary case study practitioners – and representing various strands of IR theory – have increasingly sought to clarify and develop their methodological techniques and epistemological grounding (Bennett and Elman, 2010: 499-500).

A second issue, again also incorporating issues of construct validity, concerns that of the reliability and replicability of various forms of single case study analysis. This is usually tied to a broader critique of qualitative research methods as a whole. However, whereas the latter obviously tend toward an explicitly-acknowledged interpretive basis for meanings, reasons, and understandings:

“quantitative measures appear objective, but only so long as we don’t ask questions about where and how the data were produced… pure objectivity is not a meaningful concept if the goal is to measure intangibles [as] these concepts only exist because we can interpret them” (Berg and Lune, 2010: 340).

The question of researcher subjectivity is a valid one, and it may be intended only as a methodological critique of what are obviously less formalised and researcher-independent methods (Verschuren, 2003). Owen (1994) and Layne’s (1994) contradictory process tracing results of interdemocratic war-avoidance during the Anglo-American crisis of 1861 to 1863 – from liberal and realist standpoints respectively – are a useful example. However, it does also rest on certain assumptions that can raise deeper and potentially irreconcilable ontological and epistemological issues. There are, regardless, plenty such as Bent Flyvbjerg (2006: 237) who suggest that the case study contains no greater bias toward verification than other methods of inquiry, and that “on the contrary, experience indicates that the case study contains a greater bias toward falsification of preconceived notions than toward verification”.

The third and arguably most prominent critique of single case study analysis is the issue of external validity or generalisability. How is it that one case can reliably offer anything beyond the particular? “We always do better (or, in the extreme, no worse) with more observation as the basis of our generalization”, as King et al write; “in all social science research and all prediction, it is important that we be as explicit as possible about the degree of uncertainty that accompanies out prediction” (1994: 212). This is an unavoidably valid criticism. It may be that theories which pass a single crucial case study test, for example, require rare antecedent conditions and therefore actually have little explanatory range. These conditions may emerge more clearly, as Van Evera (1997: 51-54) notes, from large-N studies in which cases that lack them present themselves as outliers exhibiting a theory’s cause but without its predicted outcome. As with the case of Indian democratisation above, it would logically be preferable to conduct large-N analysis beforehand to identify that state’s non-representative nature in relation to the broader population.

There are, however, three important qualifiers to the argument about generalisation that deserve particular mention here. The first is that with regard to an idiographic single-outcome case study, as Eckstein notes, the criticism is “mitigated by the fact that its capability to do so [is] never claimed by its exponents; in fact it is often explicitly repudiated” (1975: 134). Criticism of generalisability is of little relevance when the intention is one of particularisation. A second qualifier relates to the difference between statistical and analytical generalisation; single case studies are clearly less appropriate for the former but arguably retain significant utility for the latter – the difference also between explanatory and exploratory, or theory-testing and theory-building, as discussed above. As Gerring puts it, “theory confirmation/disconfirmation is not the case study’s strong suit” (2004: 350). A third qualification relates to the issue of case selection. As Seawright and Gerring (2008) note, the generalisability of case studies can be increased by the strategic selection of cases. Representative or random samples may not be the most appropriate, given that they may not provide the richest insight (or indeed, that a random and unknown deviant case may appear). Instead, and properly used , atypical or extreme cases “often reveal more information because they activate more actors… and more basic mechanisms in the situation studied” (Flyvbjerg, 2006). Of course, this also points to the very serious limitation, as hinted at with the case of India above, that poor case selection may alternatively lead to overgeneralisation and/or grievous misunderstandings of the relationship between variables or processes (Bennett and Elman, 2006a: 460-463).

As Tim May (2011: 226) notes, “the goal for many proponents of case studies […] is to overcome dichotomies between generalizing and particularizing, quantitative and qualitative, deductive and inductive techniques”. Research aims should drive methodological choices, rather than narrow and dogmatic preconceived approaches. As demonstrated above, there are various advantages to both idiographic and nomothetic single case study analyses – notably the empirically-rich, context-specific, holistic accounts that they have to offer, and their contribution to theory-building and, to a lesser extent, that of theory-testing. Furthermore, while they do possess clear limitations, any research method involves necessary trade-offs; the inherent weaknesses of any one method, however, can potentially be offset by situating them within a broader, pluralistic mixed-method research strategy. Whether or not single case studies are used in this fashion, they clearly have a great deal to offer.

References 

Bennett, A. and Checkel, J. T. (2012) ‘Process Tracing: From Philosophical Roots to Best Practice’, Simons Papers in Security and Development, No. 21/2012, School for International Studies, Simon Fraser University: Vancouver.

Bennett, A. and Elman, C. (2006a) ‘Qualitative Research: Recent Developments in Case Study Methods’, Annual Review of Political Science , 9, 455-476.

Bennett, A. and Elman, C. (2006b) ‘Complex Causal Relations and Case Study Methods: The Example of Path Dependence’, Political Analysis , 14, 3, 250-267.

Bennett, A. and Elman, C. (2007) ‘Case Study Methods in the International Relations Subfield’, Comparative Political Studies , 40, 2, 170-195.

Bennett, A. and Elman, C. (2010) Case Study Methods. In C. Reus-Smit and D. Snidal (eds) The Oxford Handbook of International Relations . Oxford University Press: Oxford. Ch. 29.

Berg, B. and Lune, H. (2012) Qualitative Research Methods for the Social Sciences . Pearson: London.

Bryman, A. (2012) Social Research Methods . Oxford University Press: Oxford.

David, M. and Sutton, C. D. (2011) Social Research: An Introduction . SAGE Publications Ltd: London.

Diamond, J. (1992) ‘Economic development and democracy reconsidered’, American Behavioral Scientist , 35, 4/5, 450-499.

Eckstein, H. (1975) Case Study and Theory in Political Science. In R. Gomm, M. Hammersley, and P. Foster (eds) Case Study Method . SAGE Publications Ltd: London.

Flyvbjerg, B. (2006) ‘Five Misunderstandings About Case-Study Research’, Qualitative Inquiry , 12, 2, 219-245.

Geertz, C. (1973) The Interpretation of Cultures: Selected Essays by Clifford Geertz . Basic Books Inc: New York.

Gerring, J. (2004) ‘What is a Case Study and What Is It Good for?’, American Political Science Review , 98, 2, 341-354.

Gerring, J. (2006a) Case Study Research: Principles and Practices . Cambridge University Press: Cambridge.

Gerring, J. (2006b) ‘Single-Outcome Studies: A Methodological Primer’, International Sociology , 21, 5, 707-734.

Gerring, J. (2007) ‘Is There a (Viable) Crucial-Case Method?’, Comparative Political Studies , 40, 3, 231-253.

King, G., Keohane, R. O. and Verba, S. (1994) Designing Social Inquiry: Scientific Inference in Qualitative Research . Princeton University Press: Chichester.

Layne, C. (1994) ‘Kant or Cant: The Myth of the Democratic Peace’, International Security , 19, 2, 5-49.

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MacMillan, A. (2008) ‘Deviant Democratization in India’, Democratization , 15, 4, 733-749.

Maoz, Z. (2002) Case study methodology in international studies: from storytelling to hypothesis testing. In F. P. Harvey and M. Brecher (eds) Evaluating Methodology in International Studies . University of Michigan Press: Ann Arbor.

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[1] The paper follows convention by differentiating between ‘International Relations’ as the academic discipline and ‘international relations’ as the subject of study.

[2] There is some similarity here with Stake’s (2008: 445-447) notion of intrinsic cases, those undertaken for a better understanding of the particular case, and instrumental ones that provide insight for the purposes of a wider external interest.

[3] These may be unique in the idiographic sense, or in nomothetic terms as an exception to the generalising suppositions of either probabilistic or deterministic theories (as per deviant cases, below).

[4] Although there are “philosophical hurdles to mount”, according to Bennett and Checkel, there exists no a priori reason as to why process tracing (as typically grounded in scientific realism) is fundamentally incompatible with various strands of positivism or interpretivism (2012: 18-19). By extension, it can therefore be incorporated by a range of contemporary mainstream IR theories.

— Written by: Ben Willis Written at: University of Plymouth Written for: David Brockington Date written: January 2013

Further Reading on E-International Relations

• Identity in International Conflicts: A Case Study of the Cuban Missile Crisis
• Imperialism’s Legacy in the Study of Contemporary Politics: The Case of Hegemonic Stability Theory
• Recreating a Nation’s Identity Through Symbolism: A Chinese Case Study
• Ontological Insecurity: A Case Study on Israeli-Palestinian Conflict in Jerusalem
• Terrorists or Freedom Fighters: A Case Study of ETA
• A Critical Assessment of Eco-Marxism: A Ghanaian Case Study

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Distinguishing case study as a research method from case reports as a publication type

The purpose of this editorial is to distinguish between case reports and case studies. In health, case reports are familiar ways of sharing events or efforts of intervening with single patients with previously unreported features. As a qualitative methodology, case study research encompasses a great deal more complexity than a typical case report and often incorporates multiple streams of data combined in creative ways. The depth and richness of case study description helps readers understand the case and whether findings might be applicable beyond that setting.

Single-institution descriptive reports of library activities are often labeled by their authors as “case studies.” By contrast, in health care, single patient retrospective descriptions are published as “case reports.” Both case reports and case studies are valuable to readers and provide a publication opportunity for authors. A previous editorial by Akers and Amos about improving case studies addresses issues that are more common to case reports; for example, not having a review of the literature or being anecdotal, not generalizable, and prone to various types of bias such as positive outcome bias [ 1 ]. However, case study research as a qualitative methodology is pursued for different purposes than generalizability. The authors’ purpose in this editorial is to clearly distinguish between case reports and case studies. We believe that this will assist authors in describing and designating the methodological approach of their publications and help readers appreciate the rigor of well-executed case study research.

Case reports often provide a first exploration of a phenomenon or an opportunity for a first publication by a trainee in the health professions. In health care, case reports are familiar ways of sharing events or efforts of intervening with single patients with previously unreported features. Another type of study categorized as a case report is an “N of 1” study or single-subject clinical trial, which considers an individual patient as the sole unit of observation in a study investigating the efficacy or side effect profiles of different interventions. Entire journals have evolved to publish case reports, which often rely on template structures with limited contextualization or discussion of previous cases. Examples that are indexed in MEDLINE include the American Journal of Case Reports , BMJ Case Reports, Journal of Medical Case Reports, and Journal of Radiology Case Reports . Similar publications appear in veterinary medicine and are indexed in CAB Abstracts, such as Case Reports in Veterinary Medicine and Veterinary Record Case Reports .

As a qualitative methodology, however, case study research encompasses a great deal more complexity than a typical case report and often incorporates multiple streams of data combined in creative ways. Distinctions include the investigator’s definitions and delimitations of the case being studied, the clarity of the role of the investigator, the rigor of gathering and combining evidence about the case, and the contextualization of the findings. Delimitation is a term from qualitative research about setting boundaries to scope the research in a useful way rather than describing the narrow scope as a limitation, as often appears in a discussion section. The depth and richness of description helps readers understand the situation and whether findings from the case are applicable to their settings.

CASE STUDY AS A RESEARCH METHODOLOGY

Case study as a qualitative methodology is an exploration of a time- and space-bound phenomenon. As qualitative research, case studies require much more from their authors who are acting as instruments within the inquiry process. In the case study methodology, a variety of methodological approaches may be employed to explain the complexity of the problem being studied [ 2 , 3 ].

Leading authors diverge in their definitions of case study, but a qualitative research text introduces case study as follows:

Case study research is defined as a qualitative approach in which the investigator explores a real-life, contemporary bounded system (a case) or multiple bound systems (cases) over time, through detailed, in-depth data collection involving multiple sources of information, and reports a case description and case themes. The unit of analysis in the case study might be multiple cases (a multisite study) or a single case (a within-site case study). [ 4 ]

Methodologists writing core texts on case study research include Yin [ 5 ], Stake [ 6 ], and Merriam [ 7 ]. The approaches of these three methodologists have been compared by Yazan, who focused on six areas of methodology: epistemology (beliefs about ways of knowing), definition of cases, design of case studies, and gathering, analysis, and validation of data [ 8 ]. For Yin, case study is a method of empirical inquiry appropriate to determining the “how and why” of phenomena and contributes to understanding phenomena in a holistic and real-life context [ 5 ]. Stake defines a case study as a “well-bounded, specific, complex, and functioning thing” [ 6 ], while Merriam views “the case as a thing, a single entity, a unit around which there are boundaries” [ 7 ].

Case studies are ways to explain, describe, or explore phenomena. Comments from a quantitative perspective about case studies lacking rigor and generalizability fail to consider the purpose of the case study and how what is learned from a case study is put into practice. Rigor in case studies comes from the research design and its components, which Yin outlines as (a) the study’s questions, (b) the study’s propositions, (c) the unit of analysis, (d) the logic linking the data to propositions, and (e) the criteria for interpreting the findings [ 5 ]. Case studies should also provide multiple sources of data, a case study database, and a clear chain of evidence among the questions asked, the data collected, and the conclusions drawn [ 5 ].

Sources of evidence for case studies include interviews, documentation, archival records, direct observations, participant-observation, and physical artifacts. One of the most important sources for data in qualitative case study research is the interview [ 2 , 3 ]. In addition to interviews, documents and archival records can be gathered to corroborate and enhance the findings of the study. To understand the phenomenon or the conditions that created it, direct observations can serve as another source of evidence and can be conducted throughout the study. These can include the use of formal and informal protocols as a participant inside the case or an external or passive observer outside of the case [ 5 ]. Lastly, physical artifacts can be observed and collected as a form of evidence. With these multiple potential sources of evidence, the study methodology includes gathering data, sense-making, and triangulating multiple streams of data. Figure 1 shows an example in which data used for the case started with a pilot study to provide additional context to guide more in-depth data collection and analysis with participants.

Key sources of data for a sample case study

VARIATIONS ON CASE STUDY METHODOLOGY

Case study methodology is evolving and regularly reinterpreted. Comparative or multiple case studies are used as a tool for synthesizing information across time and space to research the impact of policy and practice in various fields of social research [ 9 ]. Because case study research is in-depth and intensive, there have been efforts to simplify the method or select useful components of cases for focused analysis. Micro-case study is a term that is occasionally used to describe research on micro-level cases [ 10 ]. These are cases that occur in a brief time frame, occur in a confined setting, and are simple and straightforward in nature. A micro-level case describes a clear problem of interest. Reporting is very brief and about specific points. The lack of complexity in the case description makes obvious the “lesson” that is inherent in the case; although no definitive “solution” is necessarily forthcoming, making the case useful for discussion. A micro-case write-up can be distinguished from a case report by its focus on briefly reporting specific features of a case or cases to analyze or learn from those features.

DATABASE INDEXING OF CASE REPORTS AND CASE STUDIES

Disciplines such as education, psychology, sociology, political science, and social work regularly publish rich case studies that are relevant to particular areas of health librarianship. Case reports and case studies have been defined as publication types or subject terms by several databases that are relevant to librarian authors: MEDLINE, PsycINFO, CINAHL, and ERIC. Library, Information Science & Technology Abstracts (LISTA) does not have a subject term or publication type related to cases, despite many being included in the database. Whereas “Case Reports” are the main term used by MEDLINE’s Medical Subject Headings (MeSH) and PsycINFO’s thesaurus, CINAHL and ERIC use “Case Studies.”

Case reports in MEDLINE and PsycINFO focus on clinical case documentation. In MeSH, “Case Reports” as a publication type is specific to “clinical presentations that may be followed by evaluative studies that eventually lead to a diagnosis” [ 11 ]. “Case Histories,” “Case Studies,” and “Case Study” are all entry terms mapping to “Case Reports”; however, guidance to indexers suggests that “Case Reports” should not be applied to institutional case reports and refers to the heading “Organizational Case Studies,” which is defined as “descriptions and evaluations of specific health care organizations” [ 12 ].

PsycINFO’s subject term “Case Report” is “used in records discussing issues involved in the process of conducting exploratory studies of single or multiple clinical cases.” The Methodology index offers clinical and non-clinical entries. “Clinical Case Study” is defined as “case reports that include disorder, diagnosis, and clinical treatment for individuals with mental or medical illnesses,” whereas “Non-clinical Case Study” is a “document consisting of non-clinical or organizational case examples of the concepts being researched or studied. The setting is always non-clinical and does not include treatment-related environments” [ 13 ].

Both CINAHL and ERIC acknowledge the depth of analysis in case study methodology. The CINAHL scope note for the thesaurus term “Case Studies” distinguishes between the document and the methodology, though both use the same term: “a review of a particular condition, disease, or administrative problem. Also, a research method that involves an in-depth analysis of an individual, group, institution, or other social unit. For material that contains a case study, search for document type: case study.” The ERIC scope note for the thesaurus term “Case Studies” is simple: “detailed analyses, usually focusing on a particular problem of an individual, group, or organization” [ 14 ].

PUBLICATION OF CASE STUDY RESEARCH IN LIBRARIANSHIP

We call your attention to a few examples published as case studies in health sciences librarianship to consider how their characteristics fit with the preceding definitions of case reports or case study research. All present some characteristics of case study research, but their treatment of the research questions, richness of description, and analytic strategies vary in depth and, therefore, diverge at some level from the qualitative case study research approach. This divergence, particularly in richness of description and analysis, may have been constrained by the publication requirements.

As one example, a case study by Janke and Rush documented a time- and context-bound collaboration involving a librarian and a nursing faculty member [ 15 ]. Three objectives were stated: (1) describing their experience of working together on an interprofessional research team, (2) evaluating the value of the librarian role from librarian and faculty member perspectives, and (3) relating findings to existing literature. Elements that signal the qualitative nature of this case study are that the authors were the research participants and their use of the term “evaluation” is reflection on their experience. This reads like a case study that could have been enriched by including other types of data gathered from others engaging with this team to broaden the understanding of the collaboration.

As another example, the description of the academic context is one of the most salient components of the case study written by Clairoux et al., which had the objectives of (1) describing the library instruction offered and learning assessments used at a single health sciences library and (2) discussing the positive outcomes of instruction in that setting [ 16 ]. The authors focus on sharing what the institution has done more than explaining why this institution is an exemplar to explore a focused question or understand the phenomenon of library instruction. However, like a case study, the analysis brings together several streams of data including course attendance, online material page views, and some discussion of results from surveys. This paper reads somewhat in between an institutional case report and a case study.

The final example is a single author reporting on a personal experience of creating and executing the role of research informationist for a National Institutes of Health (NIH)–funded research team [ 17 ]. There is a thoughtful review of the informationist literature and detailed descriptions of the institutional context and the process of gaining access to and participating in the new role. However, the motivating question in the abstract does not seem to be fully addressed through analysis from either the reflective perspective of the author as the research participant or consideration of other streams of data from those involved in the informationist experience. The publication reads more like a case report about this informationist’s experience than a case study that explores the research informationist experience through the selection of this case.

All of these publications are well written and useful for their intended audiences, but in general, they are much shorter and much less rich in depth than case studies published in social sciences research. It may be that the authors have been constrained by word counts or page limits. For example, the submission category for Case Studies in the Journal of the Medical Library Association (JMLA) limited them to 3,000 words and defined them as “articles describing the process of developing, implementing, and evaluating a new service, program, or initiative, typically in a single institution or through a single collaborative effort” [ 18 ]. This definition’s focus on novelty and description sounds much more like the definition of case report than the in-depth, detailed investigation of a time- and space-bound problem that is often examined through case study research.

Problem-focused or question-driven case study research would benefit from the space provided for Original Investigations that employ any type of quantitative or qualitative method of analysis. One of the best examples in the JMLA of an in-depth multiple case study that was authored by a librarian who published the findings from her doctoral dissertation represented all the elements of a case study. In eight pages, she provided a theoretical basis for the research question, a pilot study, and a multiple case design, including integrated data from interviews and focus groups [ 19 ].

We have distinguished between case reports and case studies primarily to assist librarians who are new to research and critical appraisal of case study methodology to recognize the features that authors use to describe and designate the methodological approaches of their publications. For researchers who are new to case research methodology and are interested in learning more, Hancock and Algozzine provide a guide [ 20 ].

We hope that JMLA readers appreciate the rigor of well-executed case study research. We believe that distinguishing between descriptive case reports and analytic case studies in the journal’s submission categories will allow the depth of case study methodology to increase. We also hope that authors feel encouraged to pursue submitting relevant case studies or case reports for future publication.

Editor’s note: In response to this invited editorial, the Journal of the Medical Library Association will consider manuscripts employing rigorous qualitative case study methodology to be Original Investigations (fewer than 5,000 words), whereas manuscripts describing the process of developing, implementing, and assessing a new service, program, or initiative—typically in a single institution or through a single collaborative effort—will be considered to be Case Reports (formerly known as Case Studies; fewer than 3,000 words).

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• Perspective
• Published: 22 November 2022

Single case studies are a powerful tool for developing, testing and extending theories

• Lyndsey Nickels   ORCID: orcid.org/0000-0002-0311-3524 1 , 2 ,
• Simon Fischer-Baum   ORCID: orcid.org/0000-0002-6067-0538 3 &
• Wendy Best   ORCID: orcid.org/0000-0001-8375-5916 4  

Nature Reviews Psychology volume  1 ,  pages 733–747 ( 2022 ) Cite this article

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Psychology embraces a diverse range of methodologies. However, most rely on averaging group data to draw conclusions. In this Perspective, we argue that single case methodology is a valuable tool for developing and extending psychological theories. We stress the importance of single case and case series research, drawing on classic and contemporary cases in which cognitive and perceptual deficits provide insights into typical cognitive processes in domains such as memory, delusions, reading and face perception. We unpack the key features of single case methodology, describe its strengths, its value in adjudicating between theories, and outline its benefits for a better understanding of deficits and hence more appropriate interventions. The unique insights that single case studies have provided illustrate the value of in-depth investigation within an individual. Single case methodology has an important place in the psychologist’s toolkit and it should be valued as a primary research tool.

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The authors thank all of those pioneers of and advocates for single case study research who have mentored, inspired and encouraged us over the years, and the many other colleagues with whom we have discussed these issues.

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Nickels, L., Fischer-Baum, S. & Best, W. Single case studies are a powerful tool for developing, testing and extending theories. Nat Rev Psychol 1 , 733–747 (2022). https://doi.org/10.1038/s44159-022-00127-y

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Case Study Research Method in Psychology

Saul Mcleod, PhD

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On This Page:

Case studies are in-depth investigations of a person, group, event, or community. Typically, data is gathered from various sources using several methods (e.g., observations & interviews).

The case study research method originated in clinical medicine (the case history, i.e., the patient’s personal history). In psychology, case studies are often confined to the study of a particular individual.

The information is mainly biographical and relates to events in the individual’s past (i.e., retrospective), as well as to significant events that are currently occurring in his or her everyday life.

The case study is not a research method, but researchers select methods of data collection and analysis that will generate material suitable for case studies.

Freud (1909a, 1909b) conducted very detailed investigations into the private lives of his patients in an attempt to both understand and help them overcome their illnesses.

This makes it clear that the case study is a method that should only be used by a psychologist, therapist, or psychiatrist, i.e., someone with a professional qualification.

There is an ethical issue of competence. Only someone qualified to diagnose and treat a person can conduct a formal case study relating to atypical (i.e., abnormal) behavior or atypical development.

 Famous Case Studies

• Anna O – One of the most famous case studies, documenting psychoanalyst Josef Breuer’s treatment of “Anna O” (real name Bertha Pappenheim) for hysteria in the late 1800s using early psychoanalytic theory.
• Little Hans – A child psychoanalysis case study published by Sigmund Freud in 1909 analyzing his five-year-old patient Herbert Graf’s house phobia as related to the Oedipus complex.
• Bruce/Brenda – Gender identity case of the boy (Bruce) whose botched circumcision led psychologist John Money to advise gender reassignment and raise him as a girl (Brenda) in the 1960s.
• Genie Wiley – Linguistics/psychological development case of the victim of extreme isolation abuse who was studied in 1970s California for effects of early language deprivation on acquiring speech later in life.
• Phineas Gage – One of the most famous neuropsychology case studies analyzes personality changes in railroad worker Phineas Gage after an 1848 brain injury involving a tamping iron piercing his skull.

Clinical Case Studies

• Studying the effectiveness of psychotherapy approaches with an individual patient
• Assessing and treating mental illnesses like depression, anxiety disorders, PTSD
• Neuropsychological cases investigating brain injuries or disorders

Child Psychology Case Studies

• Studying psychological development from birth through adolescence
• Cases of learning disabilities, autism spectrum disorders, ADHD
• Effects of trauma, abuse, deprivation on development

Types of Case Studies

• Explanatory case studies : Used to explore causation in order to find underlying principles. Helpful for doing qualitative analysis to explain presumed causal links.
• Exploratory case studies : Used to explore situations where an intervention being evaluated has no clear set of outcomes. It helps define questions and hypotheses for future research.
• Descriptive case studies : Describe an intervention or phenomenon and the real-life context in which it occurred. It is helpful for illustrating certain topics within an evaluation.
• Multiple-case studies : Used to explore differences between cases and replicate findings across cases. Helpful for comparing and contrasting specific cases.
• Intrinsic : Used to gain a better understanding of a particular case. Helpful for capturing the complexity of a single case.
• Collective : Used to explore a general phenomenon using multiple case studies. Helpful for jointly studying a group of cases in order to inquire into the phenomenon.

Where Do You Find Data for a Case Study?

There are several places to find data for a case study. The key is to gather data from multiple sources to get a complete picture of the case and corroborate facts or findings through triangulation of evidence. Most of this information is likely qualitative (i.e., verbal description rather than measurement), but the psychologist might also collect numerical data.

1. Primary sources

• Interviews – Interviewing key people related to the case to get their perspectives and insights. The interview is an extremely effective procedure for obtaining information about an individual, and it may be used to collect comments from the person’s friends, parents, employer, workmates, and others who have a good knowledge of the person, as well as to obtain facts from the person him or herself.
• Observations – Observing behaviors, interactions, processes, etc., related to the case as they unfold in real-time.
• Documents & Records – Reviewing private documents, diaries, public records, correspondence, meeting minutes, etc., relevant to the case.

2. Secondary sources

• News/Media – News coverage of events related to the case study.
• Academic articles – Journal articles, dissertations etc. that discuss the case.
• Government reports – Official data and records related to the case context.
• Books/films – Books, documentaries or films discussing the case.

3. Archival records

Searching historical archives, museum collections and databases to find relevant documents, visual/audio records related to the case history and context.

Public archives like newspapers, organizational records, photographic collections could all include potentially relevant pieces of information to shed light on attitudes, cultural perspectives, common practices and historical contexts related to psychology.

4. Organizational records

Organizational records offer the advantage of often having large datasets collected over time that can reveal or confirm psychological insights.

Of course, privacy and ethical concerns regarding confidential data must be navigated carefully.

However, with proper protocols, organizational records can provide invaluable context and empirical depth to qualitative case studies exploring the intersection of psychology and organizations.

• Organizational/industrial psychology research : Organizational records like employee surveys, turnover/retention data, policies, incident reports etc. may provide insight into topics like job satisfaction, workplace culture and dynamics, leadership issues, employee behaviors etc.
• Clinical psychology : Therapists/hospitals may grant access to anonymized medical records to study aspects like assessments, diagnoses, treatment plans etc. This could shed light on clinical practices.
• School psychology : Studies could utilize anonymized student records like test scores, grades, disciplinary issues, and counseling referrals to study child development, learning barriers, effectiveness of support programs, and more.

How do I Write a Case Study in Psychology?

Follow specified case study guidelines provided by a journal or your psychology tutor. General components of clinical case studies include: background, symptoms, assessments, diagnosis, treatment, and outcomes. Interpreting the information means the researcher decides what to include or leave out. A good case study should always clarify which information is the factual description and which is an inference or the researcher’s opinion.

1. Introduction

• Provide background on the case context and why it is of interest, presenting background information like demographics, relevant history, and presenting problem.
• Compare briefly to similar published cases if applicable. Clearly state the focus/importance of the case.

2. Case Presentation

• Describe the presenting problem in detail, including symptoms, duration,and impact on daily life.
• Include client demographics like age and gender, information about social relationships, and mental health history.
• Describe all physical, emotional, and/or sensory symptoms reported by the client.
• Use patient quotes to describe the initial complaint verbatim. Follow with full-sentence summaries of relevant history details gathered, including key components that led to a working diagnosis.
• Summarize clinical exam results, namely orthopedic/neurological tests, imaging, lab tests, etc. Note actual results rather than subjective conclusions. Provide images if clearly reproducible/anonymized.
• Clearly state the working diagnosis or clinical impression before transitioning to management.

3. Management and Outcome

• Indicate the total duration of care and number of treatments given over what timeframe. Use specific names/descriptions for any therapies/interventions applied.
• Present the results of the intervention,including any quantitative or qualitative data collected.
• For outcomes, utilize visual analog scales for pain, medication usage logs, etc., if possible. Include patient self-reports of improvement/worsening of symptoms. Note the reason for discharge/end of care.

4. Discussion

• Analyze the case, exploring contributing factors, limitations of the study, and connections to existing research.
• Analyze the effectiveness of the intervention,considering factors like participant adherence, limitations of the study, and potential alternative explanations for the results.
• Identify any questions raised in the case analysis and relate insights to established theories and current research if applicable. Avoid definitive claims about physiological explanations.
• Offer clinical implications, and suggest future research directions.

5. Additional Items

• Thank specific assistants for writing support only. No patient acknowledgments.
• References should directly support any key claims or quotes included.
• Use tables/figures/images only if substantially informative. Include permissions and legends/explanatory notes.
• Provides detailed (rich qualitative) information.
• Provides insight for further research.
• Permitting investigation of otherwise impractical (or unethical) situations.

Case studies allow a researcher to investigate a topic in far more detail than might be possible if they were trying to deal with a large number of research participants (nomothetic approach) with the aim of ‘averaging’.

Because of their in-depth, multi-sided approach, case studies often shed light on aspects of human thinking and behavior that would be unethical or impractical to study in other ways.

Research that only looks into the measurable aspects of human behavior is not likely to give us insights into the subjective dimension of experience, which is important to psychoanalytic and humanistic psychologists.

Case studies are often used in exploratory research. They can help us generate new ideas (that might be tested by other methods). They are an important way of illustrating theories and can help show how different aspects of a person’s life are related to each other.

The method is, therefore, important for psychologists who adopt a holistic point of view (i.e., humanistic psychologists ).

Limitations

• Lacking scientific rigor and providing little basis for generalization of results to the wider population.
• Researchers’ own subjective feelings may influence the case study (researcher bias).
• Difficult to replicate.
• Time-consuming and expensive.
• The volume of data, together with the time restrictions in place, impacted the depth of analysis that was possible within the available resources.

Because a case study deals with only one person/event/group, we can never be sure if the case study investigated is representative of the wider body of “similar” instances. This means the conclusions drawn from a particular case may not be transferable to other settings.

Because case studies are based on the analysis of qualitative (i.e., descriptive) data , a lot depends on the psychologist’s interpretation of the information she has acquired.

This means that there is a lot of scope for Anna O , and it could be that the subjective opinions of the psychologist intrude in the assessment of what the data means.

For example, Freud has been criticized for producing case studies in which the information was sometimes distorted to fit particular behavioral theories (e.g., Little Hans ).

This is also true of Money’s interpretation of the Bruce/Brenda case study (Diamond, 1997) when he ignored evidence that went against his theory.

Breuer, J., & Freud, S. (1895).  Studies on hysteria . Standard Edition 2: London.

Curtiss, S. (1981). Genie: The case of a modern wild child .

Diamond, M., & Sigmundson, K. (1997). Sex Reassignment at Birth: Long-term Review and Clinical Implications. Archives of Pediatrics & Adolescent Medicine , 151(3), 298-304

Freud, S. (1909a). Analysis of a phobia of a five year old boy. In The Pelican Freud Library (1977), Vol 8, Case Histories 1, pages 169-306

Freud, S. (1909b). Bemerkungen über einen Fall von Zwangsneurose (Der “Rattenmann”). Jb. psychoanal. psychopathol. Forsch ., I, p. 357-421; GW, VII, p. 379-463; Notes upon a case of obsessional neurosis, SE , 10: 151-318.

Harlow J. M. (1848). Passage of an iron rod through the head.  Boston Medical and Surgical Journal, 39 , 389–393.

Harlow, J. M. (1868).  Recovery from the Passage of an Iron Bar through the Head .  Publications of the Massachusetts Medical Society. 2  (3), 327-347.

Money, J., & Ehrhardt, A. A. (1972).  Man & Woman, Boy & Girl : The Differentiation and Dimorphism of Gender Identity from Conception to Maturity. Baltimore, Maryland: Johns Hopkins University Press.

Money, J., & Tucker, P. (1975). Sexual signatures: On being a man or a woman.

Further Information

• Case Study Approach
• Case Study Method
• Enhancing the Quality of Case Studies in Health Services Research
• “We do things together” A case study of “couplehood” in dementia
• Using mixed methods for evaluating an integrative approach to cancer care: a case study

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Qualitative Data Coding

What Is a Focus Group?

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What Is Internal Validity In Research?

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What Is Face Validity In Research? Importance & How To Measure

Criterion Validity: Definition & Examples

Quantitative study designs: Case Studies/ Case Report/ Case Series

Quantitative study designs.

• Introduction
• Cohort Studies
• Randomised Controlled Trial
• Case Control
• Cross-Sectional Studies
• Study Designs Home

Case Study / Case Report / Case Series

Some famous examples of case studies are John Martin Marlow’s case study on Phineas Gage (the man who had a railway spike through his head) and Sigmund Freud’s case studies, Little Hans and The Rat Man. Case studies are widely used in psychology to provide insight into unusual conditions.

A case study, also known as a case report, is an in depth or intensive study of a single individual or specific group, while a case series is a grouping of similar case studies / case reports together.

A case study / case report can be used in the following instances:

• where there is atypical or abnormal behaviour or development
• an unexplained outcome to treatment
• an emerging disease or condition

The stages of a Case Study / Case Report / Case Series

Which clinical questions does Case Study / Case Report / Case Series best answer?

Emerging conditions, adverse reactions to treatments, atypical / abnormal behaviour, new programs or methods of treatment – all of these can be answered with case studies /case reports / case series. They are generally descriptive studies based on qualitative data e.g. observations, interviews, questionnaires, diaries, personal notes or clinical notes.

What are the advantages and disadvantages to consider when using Case Studies/ Case Reports and Case Series ?

What are the pitfalls to look for.

One pitfall that has occurred in some case studies is where two common conditions/treatments have been linked together with no comprehensive data backing up the conclusion. A hypothetical example could be where high rates of the common cold were associated with suicide when the cohort also suffered from depression.

Critical appraisal tools 

To assist with critically appraising Case studies / Case reports / Case series there are some tools / checklists you can use.

JBI Critical Appraisal Checklist for Case Series

JBI Critical Appraisal Checklist for Case Reports

Real World Examples

Some Psychology case study / case report / case series examples

Capp, G. (2015). Our community, our schools : A case study of program design for school-based mental health services. Children & Schools, 37(4), 241–248. A pilot program to improve school based mental health services was instigated in one elementary school and one middle / high school. The case study followed the program from development through to implementation, documenting each step of the process.

Cowdrey, F. A. & Walz, L. (2015). Exposure therapy for fear of spiders in an adult with learning disabilities: A case report. British Journal of Learning Disabilities, 43(1), 75–82. One person was studied who had completed a pre- intervention and post- intervention questionnaire. From the results of this data the exposure therapy intervention was found to be effective in reducing the phobia. This case report highlighted a therapy that could be used to assist people with learning disabilities who also suffered from phobias.

Li, H. X., He, L., Zhang, C. C., Eisinger, R., Pan, Y. X., Wang, T., . . . Li, D. Y. (2019). Deep brain stimulation in post‐traumatic dystonia: A case series study. CNS Neuroscience & Therapeutics. 1-8. Five patients were included in the case series, all with the same condition. They all received deep brain stimulation but not in the same area of the brain. Baseline and last follow up visit were assessed with the same rating scale.

References and Further Reading  

Greenhalgh, T. (2014). How to read a paper: the basics of evidence-based medicine. (5th ed.). New York: Wiley.

Heale, R. & Twycross, A. (2018). What is a case study? Evidence Based Nursing, 21(1), 7-8.

Himmelfarb Health Sciences Library. (2019). Study design 101: case report. Retrieved from https://himmelfarb.gwu.edu/tutorials/studydesign101/casereports.cfm

Hoffmann T., Bennett S., Mar C. D. (2017). Evidence-based practice across the health professions. Chatswood, NSW: Elsevier.

Robinson, O. C., & McAdams, D. P. (2015). Four functional roles for case studies in emerging adulthood research. Emerging Adulthood, 3(6), 413-420.

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Multiple Case Research Design

• First Online: 10 November 2021

Cite this chapter

• Stefan Hunziker 3 &
• Michael Blankenagel 3  

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This chapter addresses the peculiarities, characteristics, and major fallacies of multiple case research designs. The major advantage of multiple case research lies in cross-case analysis. A multiple case research design shifts the focus from understanding a single case to the differences and similarities between cases. Thus, it is not just conducting more (second, third, etc.) case studies. Rather, it is the next step in developing a theory about factors driving differences and similarities. Also, researchers find relevant information on how to write a multiple case research design paper and learn about typical methodologies used for this research design. The chapter closes with referring to overlapping and adjacent research designs.

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Hunziker, S., Blankenagel, M. (2021). Multiple Case Research Design. In: Research Design in Business and Management. Springer Gabler, Wiesbaden. https://doi.org/10.1007/978-3-658-34357-6_9

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Case Study Research: Single or Multiple?

Https://doi.org/10.5281/zenodo.7106698.

Definition of a Case Study

A case study is a methodological research approach used to generate an in-depth understanding of a contemporary issue or phenomenon in a bounded system.

A case study is one of the most widely used and accepted means of qualitative research methods in the social sciences (Bloomberg & Volpe, 2022). The case study approach is particularly useful to employ when there is a need to obtain an in-depth appreciation of an issue, event or phenomenon of interest, in its natural real-life context (Crowe et al., 2011). Case studies provide researchers with an opportunity for greater depth of understanding of an issue (Stake, 2010). The case study design is preferred as a research strategy when “how,” “why,” and “what” questions are the interest of the researcher (Yin, 2018).

The two most prominent case study scholars are Robert E. Stake and Robert K. Yin. While case study research has been conducted for some time, Stake established accepted procedures for case study research in 1995 and has produced numerous articles and books about case study methodology and analysis. Two of Stake’s works that continue to impact the academic community are his books, “The Art of Case Study Research,” and, “Multiple Case Study Analysis.” Yin emerged as a leading scholar in case study research and is still producing academic literature today, as he utilizes both quantitative and qualitative approaches to the methodology. Yin’s significant contributions to the development of case study research includes the titles, “Case Study Research and Applications: Designs and Methods,” “Applications of Case Study Research,” and, “The Case Study Anthology.”

Characteristics of a Case Study

• The identification of a case is bounded (a case within a bounded system, which means what is being studied can be defined or described within specific parameters (Creswell & Poth, 2018). A case must be bounded by time and place.
• A case study should provide an in-depth understanding of the case.
• Data is collected through various means, including interviews, focus groups, field notes, documents, autobiographies, historical documents, videos, and more.
• Data analysis differs depending on the case under study. In fact, many case studies are both qualitative and quantitative.
• The successful identification of themes is critical to producing effective descriptions in case study research.
• Case studies offer conclusions provided by the researcher regarding the meaning derived from the case and are important because case studies have continuity in nature.

Types of Case Studies

Case studies are typically defined by the intent of the case analysis. There are three types of case studies: (single) instrumental case study, collective (multiple) case study, and intrinsic case study.

In a single instrumental case study, the researcher focuses on an issue or concern and then selects one bounded case to illustrate the issue (Creswell & Poth, 2018). If the researcher only wants to study one single thing (such as single person from a specific group) or a single group (for example a specific group of people within a bounded system), a single case study is the best choice (Yin, 2017).

In a multiple case study. the researcher selects multiple cases to illustrate the one issue or concern (Creswell & Poth, 2018). Multiple case studies can be used to either augur contrasting results for expected reasons or augur similar results in the studies (Yin, 2017).

In an intrinsic case study, the focus is on the case itself because the case presents a unique situation, thus resembling the focus of narrative research but maintaining the analytic procedures of a case study (Creswell & Poth, 2018).

Bloomberg, L. D., & Volpe, M. (2022).  Completing your qualitative dissertation: A road map from beginning to end . SAGE.

Creswell, J. W., & Poth, C. N. (2018).  Qualitative inquiry and research design: Choosing among five approaches . SAGE.

Crowe, S., Cresswell, K., Robertson, A., Huby, G., Avery, A., & Sheikh, A. (2011). The case study approach.  BMC medical research methodology ,  11 , 100.  https://doi.org/10.1186/1471-2288-11-100 .

Stake, R. E. (2010).  The art of case study research . SAGE.

Yin, R. K. (2018).  Case Study Research and Applications: Designs and Methods  (6th ed.). Sage.

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Scientists may have finally solved the problem of the universe’s 'missing' black holes

Primordial black holes are one of the strongest candidates for the universe's missing dark matter. But a new theory suggests that not enough of the miniature black holes formed for this to be the case.

The early universe contained far fewer miniature black holes than previously thought, making the origins of our cosmos's missing matter an even greater mystery, a new study has suggested.

Miniature, or primordial, black holes (PBHs) are black holes thought to have formed in the first fractions of a second after the Big Bang. According to leading theories, these dime-sized singularities popped into existence from rapidly collapsing regions of thick, hot gas.

The pockets of infinitely dense space-time are how many physicists explain the universe's dark matter, a mysterious entity that, despite being completely invisible, makes the universe much heavier than can be explained by the matter we see. 

But even though the hypothesis is popular, it has one big problem: we've yet to directly observe any primordial black holes. Now, a new study has offered a possible explanation as to why they didn't form, throwing open cosmology's dark matter problem to wider speculation. 

According to the research, the modern universe could have taken shape with far fewer primordial black holes than previous models estimated. The researchers published their findings May 29 in the journal Physical Review Letters .

Related: 1st detection of 'hiccupping' black hole leads to surprising discovery of 2nd black hole orbiting around it

"Many researchers feel they [primordial black holes] are a strong candidate for dark matter, but there would need to be plenty of them to satisfy that theory," lead author Jason Kristiano , a graduate student in theoretical physics at the University of Tokyo, said in a statement . "They are interesting for other reasons too, as since the recent innovation of gravitational wave astronomy, there have been discoveries of binary black hole mergers, which can be explained if PBHs exist in large numbers. But despite these strong reasons for their expected abundance, we have not seen any directly, and now we have a model which should explain why this is the case."

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 A hole in the picture  

The universe began 13.8 billion years ago with the Big Bang , causing the young cosmos to explode outward due to an invisible force known as dark energy . 

As the universe grew, ordinary matter, which interacts with light, congealed around clumps of invisible dark matter to create the first galaxies, connected together by a vast cosmic web. Nowadays, cosmologists think that ordinary matter, dark matter and dark energy make up about 5%, 25% and 70% of the universe’s composition, respectively.

Initially, the universe was opaque, a plasma broth that no light could traverse without being snared by electromagnetic fields produced by moving charges. Yet after 380,000 years of cooling and expansion, the plasma eventually recombined into neutral matter, giving off microwave static that became the universe's first light, the cosmic microwave background (CMB).

Cosmologists have been searching for these early black holes by studying this first baby picture of the universe . Yet, so far, none have been found.

Some physicists think there's a possibility they haven't discovered the vast numbers of primordial black holes necessary to account for dark matter simply because they've yet to learn how to detect them.

But by applying a model built on an advanced form of quantum mechanics called quantum field theory to the problem, the researchers behind the new study arrived at a different conclusion — we can't find any primordial black holes because most of them simply aren't there.

— Scientists reveal largest map of the universe's active supermassive black holes ever created

— Universe's oldest X-ray-spitting quasar could reveal how the biggest black holes were born

— Mysterious 'ancient heart' of the Milky Way discovered using Gaia probe  

Primordial black holes are believed to have emerged from the collapse of short but strong gravitational waves rippling across the universe. By applying their model to these waves, the researchers found that it could take much less of these waves to combine than other theories estimate in order to shape larger structures across the universe. And the fewer the waves necessary to recreate the picture, the fewer primordial black holes.

"It is widely believed that the collapse of short but strong wavelengths in the early universe is what creates primordial black holes," said Kristiano. "Our study suggests there should be far fewer PBHs than would be needed if they are indeed a strong candidate for dark matter or gravitational wave events."

To confirm their theory, the researchers will look to future, hyper-sensitive gravitational wave detectors such as the Laser Interferometer Space Antenna (LISA) project , which is due to be sent into space on an Ariane 3 rocket in 2035.

Ben Turner is a U.K. based staff writer at Live Science. He covers physics and astronomy, among other topics like tech and climate change. He graduated from University College London with a degree in particle physics before training as a journalist. When he's not writing, Ben enjoys reading literature, playing the guitar and embarrassing himself with chess.

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Single case studies vs. multiple case studies: A comparative study

There are several different definitions and kinds of case studies. Because of different reasons the case studies can be either single or multiple. This study attempts to answer when to write a single case study and when to write a multiple case study. It will further answer the benefits and disadvantages with the different types. The literature review, which is based on secondary sources, is about case studies. Then the literature review is discussed and analysed to reach a conclusion. The conclusion is that there are several different opinions if a single case study or a multiple case study is the best choice. Different causes to consider in the choice to make a single case study or a multiple case study are presented. Some causes are that the amount depends on the context, upon how much is known and how much new information the cases bring. Another conclusion from the case studies I looked among is that it is generally more number of pages in the multiple case studies than in the ...

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Investigating racial/ethnic differences in procedure experience in obstetrics & gynecology trainees at a single academic institution: a retrospective cohort study

• Patricia GiglioAyers 1 , 2 ,
• Christine E. Foley 1 , 2 ,
• Beth Cronin 1 , 2 &
• Dayna Burrell 1 , 2  

BMC Medical Education volume  24 , Article number:  561 ( 2024 ) Cite this article

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Discrimination is common in medical education. Resident physicians of races and ethnicities underrepresented in medicine experience daily discrimination which has been proven to negatively impact training. There is limited data on the impact of resident race/ethnicity on OB/GYN surgical training. The objective of this study was to investigate the impact of race/ethnicity on procedural experience in OB/GYN training.

A retrospective analysis of graduated OB/GYN resident case logs from 2009 to 2019 was performed at a single urban academic institution. Self-reported race/ethnicity data was collected. Association between URM and non-URM were analyzed using t-tests. Trainees were categorized by self-reported race/ethnicity into underrepresented in medicine (URM) (Black, Hispanic, Native American) and non-URM (White, Asian).

The cohort consisted of 84 residents: 19% URM ( N  = 16) and 79% non-URM ( n  = 66). Difference between URM and non-URM status and average case volume was analyzed using t-tests. There was no difference between non-URM and URM trainees and reported mean number of Total GYN (349 vs. 334, p  = 0.31) and Total OB (624 vs. 597, P  = 0.11) case logs. However, compared with non-URM, on average URM performed fewer Total procedures (1562 vs. 1469, P  = 0.04). Analyzing individual procedures showed a difference in average number of abortions performed between URM and non-URM (76 vs. 53, P  = 0.02). There were no other statistically significant differences between the two groups.

Conclusions

This single institution study highlights potential differences in trainee experience by race/ethnicity. Larger national studies are warranted to further explore these differences to identify bias and discrimination, and to ensure equitable experience for all trainees.

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Introduction

Discrimination is common in medical education, with nearly 60% of medical trainees experiencing at least one form of harassment or discrimination during their training [ 1 ]. Race/ethnicity has been proven to negatively impact medical student experiences and evaluations [ 2 , 3 ]. Although data remains limited, a rising number of studies explore the impact of race/ethnicity on residency training.

Resident physicians of races & ethnicities underrepresented in medicine endure daily microaggressions and biases [ 4 ]. In general surgery, up to 24% of residents report experiencing discrimination based on race/ethnicity or religion, with highest rates (70%) reported among Black residents [ 5 , 6 , 7 ]. Black surgical residents are 4.2 times more likely to experience high levels of perceived daily discrimination [ 7 ]. Discriminatory acts include being mistaken for another person of the same race, mistaken for nonphysicians, and experiencing different standards of evaluation [ 5 ]. Compared with their White counterparts, non-White residents experience increase feelings of isolation and judgement [ 8 ]. Surgical residents who experience discrimination also reported higher rates of burnout, thoughts of attrition, and suicidal thoughts [ 5 , 6 ]. A recent study investigating the relationship between gender, race/ethnicity and general surgery resident case volume cites a correlation between racial/ethnic categories underrepresented in medicine (URM) (identified as Black, Hispanic or Native American) and lower operative volumes at graduation [ 9 ].

Data regarding the impact of race/ethnicity on training in Obstetrics and Gynecology (OB/GYN) is limited. OB/GYN is reported to have the highest percentage of trainees from racial and ethnic backgrounds underrepresented in medicine at 19% among the surgical subspecialties [ 10 ]. However, recent data from 2022 demonstrated there is a greater proportion of White physicians at the fellowship level compared to residency level [ 11 ]. This trend persists in academic medicine, with a higher proportion of white physicians in leadership positions and with higher academic ranks [ 12 ]. Despite multiple initiatives by national organizations within OB/GYN to address racial and ethnic disparities [ 13 , 14 ], studies exploring racial disparities and discrimination are sparse in OB/GYN literature. To the authors knowledge, there is no published data on the impact of race/ethnicity on resident surgical training in OB/GYN. Specifically, there is no data on the impact of race on the fundamental metric of surgical volume during gynecology residency training. The aim of this study was to begin by exploring the impact of race/ethnicity on OB/GYN procedural experience in residency training at a single institution.

A retrospective analysis of graduated OB/GYN resident procedural case logs per the Accreditation Council for Graduate Medical Education (ACGME) from 2009 to 2019 at a single institution was performed. The research was deemed exempt by the IRB and was determined to be non-human subjects research. Self-reported race/ethnicity as limited by ERAS check boxes was collected. Trainees were categorized into URM (Black, Hispanic, Native American) and non-URM (White, Asian). The institution instructs residents to log a procedure if active participation as the primary surgeon is > 50% of the procedure. The primary outcome was total number of surgical procedures logged by a graduating resident. Secondary outcomes included procedure logs for the following ACGME categories: Normal spontaneous vaginal delivery (NSVD), Cesarean section (CS), Operative delivery (ODEL), Abdominal hysterectomy (AHYST), Vaginal hysterectomy (VHYST), Laparoscopic hysterectomy (LHYST), Minimally Invasive Hysterectomy (MIH), Total Hysterectomy (THYST), Incontinence and pelvic floor (ISPF), Laparoscopy (LAPS), Operative Hysteroscopy (OHYST), Abortion (ABORT), Transvaginal ultrasound (TVUS), Surgery for invasive cancer (SIC). Total numbers of cases, total obstetric (Total OB: CS, NSVD, ODEL), and total gynecologic (Total GYN: THYST, LAPS, OHYST) cases were collected. Residents in OB/GYN who completed the four-year residency training program were included in the analysis. Trainees who transferred training programs during residency or did not complete residency were excluded. Procedures were reported as mean number of procedures per ACGME category per group (URM vs. non-URM). Differences between URM and non-URM status and mean case volumes were analyzed using t-tests.

The cohort consisted of 84 residents. Residents who self-selected the ACGME category of “none of the above” ( n  = 2) were excluded from the URM vs. non-URM analyses. There was a total of 82 residents included in the final analysis: 66 non-URM (78.57%). (Table  1 ) There were no differences between non-URM and URM trainees and reported mean number of Total GYN (349 vs. 334, p  = 0.31) and Total OB (624 vs. 597, P  = 0.11) case logs. However, URM trainees had significantly fewer Total procedures (1469 vs. 1562, P  = 0.04) than their non-URM counterparts (Table  2 ). Analyzing specific procedures showed when comparing mean number of abortions, URM trainees experienced significantly less abortions (76 vs. 53, P  = 0.02) than non-URM trainees. No differences were found between non-URM and URM trainees in all other specific individual procedure categories (Table  2 ).

Resident trainees from races and ethnicities underrepresented in medicine experience daily discrimination, however there is limited data on the impact of racial/ethnic discrimination on training and postgraduate experience within OB/GYN. The importance of identifying and addressing racial and ethnic disparities within OB/GYN and medical education is widely accepted. In 2021, the ACGME launched ACGME Equity Matters, an initiative focused on learning and improvement in areas of diversity, equity and incision, and antiracism practices [ 13 ]. In 2020 ACOG, along with leading national and international women’s health organizations, released a joint statement, “Collective Action Addressing Racism.” [ 14 ] This statement specifically cites commitment to education, recognition, and scholarship as ways to eliminate inequalities in women’s health. Despite these initiatives, published research is limited.

This single institution study highlights potential differences in trainee experience by race/ethnicity and calls for further review at training programs across our specialty. This study showed a difference in total procedure experience between URM and non-URM OB/GYN residents during the 10-year time period examined. These differences may suggest discriminatory practices which are limiting procedural experience for URM residents. These findings are similar to recently published data that demonstrated a correlation between general surgery residents underrepresented in medicine or who identified as female, and lower operative volumes at graduation [ 9 ].

Additionally, this study observed a significant difference in the number of abortion procedures logged by URM versus non-URM trainees. In our institution, trainees have the choice to opt out of abortion procedures. This choice is not recorded as a part of the operative log but may confound this particular data point. We are unaware of any correlation between a trainee’s self-identified race and choice to perform abortion procedures. Additional work is needed to evaluate the demonstrated differences on a qualitative level to better identify the root cause(s) of the variation demonstrated, including possible sociocultural influences. Further work must be done to identify unconscious and overt biases and address discrimination to ensure all residents, regardless of race/ethnicity or gender, have an equitable training experience.

This small, single institution study calls for further review of racial and ethnic differences in procedural experience at training programs across our specialty. Although OB/GYN does have the highest percent of URM trainees among the surgical subspecialties, the lower proportion of URM physicians in fellowships and in higher academic rank positions suggests persistent institutional and structural racism. Procedural case logs are an objective and nationally utilized measure which could be further analyzed to identify and ultimately address training differences. If publicly available, these case logs could hold programs accountable for ensuring equitable procedural experience. Addressing any identified differences would not only improve resident experience and skill, but also contribute to the goal of creating a racially and ethnically diverse workforce to improve patient care in OB/GYN.

There are several limitations to this study, including variation in the accuracy and reporting practices of resident procedure logs which may impact data. Although criteria at this institution exist instructing residents to log only procedures which they performed > 50% of as the primary surgeon, residents are individually responsible for tracking and logging procedures. Furthermore, the small sample size of this study at a single institution, coupled with the variation in resident surgical experience and reporting practices between OB/GYN programs nationally, prevent this study from generalizability to all OB/GYN residency programs. This study analyzes total case logs at time of graduation, and therefore does not explore how race/ethnicity may impact procedural experience across the four years of residency and does not account for variation in logging during different times of residency. The authors also recognize that increased procedural numbers do not necessarily translate to procedural competency. Although differences may suggest training inequity among URM vs. non-URM residents, variation in procedural numbers may not reflect trainee competency at time of graduation.

Differences may exist in Obstetrics and Gynecology procedural experience by trainee race/ethnicity. Larger national studies are warranted to further explore these differences to identify bias and discrimination, and to ensure equitable experience for all trainees.

Data availability

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

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PGA and DB were involved in the conception, design, interpretation of data, and manuscript writing. CF was involved in the design of this study, analysis, and editing of the manuscript. BC contributed to the conception, design, and editing of this work. All authors read and approved the final manuscript.

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The ethical approval for the study and informed consent are waived by the Women and Infants Institutional Review Board due to retrospective nature of the study. All methods carried out in the study were performed in accordance with relevant guidelines and regulations.

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The author(s) declare(s) that they have no competing interests. Dr. Dayna Burrell has acted as a BMC Education article review in the past upon request. This data was accepted for oral presentation at the 2023 CREOG and APGO Annual Meeting. The conference took place February 27-March 1, 2023 in National Harbor, Maryland.

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GiglioAyers, P., Foley, C.E., Cronin, B. et al. Investigating racial/ethnic differences in procedure experience in obstetrics & gynecology trainees at a single academic institution: a retrospective cohort study. BMC Med Educ 24 , 561 (2024). https://doi.org/10.1186/s12909-024-05363-9

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DOI : https://doi.org/10.1186/s12909-024-05363-9

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• Race/Ethnicity
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Using 2% PVPI topical solution for serial intravitreous injections and ocular surface findings: a case control study

• José Henrique Casemiro 1 ,
• Ana Paula Miyagusko Taba Oguido 2 &
• Antonio Marcelo Barbante Casella 3  

International Journal of Retina and Vitreous volume  10 , Article number:  41 ( 2024 ) Cite this article

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The use of povidone-iodine for ocular surface asepsis is widespread for intravitreal injections. They became frequent procedures, leading to serial exposure of patients’ eyes to iodinated solutions. In this study, we investigate the changes in the ocular surface in patients submitted to repeated use of povidine for intravitreal injection of anti-VEGF asepsis, analyzing Ocular Surface Disease Index, non-invasive break up time, blinking quality, lipid layer, meniscus height and osmolarity.

This case-control study included 34 individuals (68 eyes), 14 males, 20 females aged 48 to 94. Inclusion criteria were individuals who received application of 2% povidone-iodine eyedrops for intravitreal injections treatment with the non-treated contralateral eye used as control. Ocular surface examinations were performed at a single occasion. A pre-intravitreal injection asepsis protocol with povidone-iodine was applied. All statistical analysis was performed using the STATA® 18.0 Software and a p-value = 0.05 was considered as the statistical significance value in all tests.

The median number of IVIs in treated eyes was 12 (range 6–20). The results in treated eyes compared with untreated eyes were respectively : median OSDI 16 (IQR 6–39) and 12.5 (IQR 8–39) ( p  = 0.380); mean NIBUT 10.30 (SD ± 2.62) and 10.78 (SD ± 2.92) ( s, p  = 0.476); median blinking quality 100 (IQR 100) and 100 (IQR 100 ) (%, p  = 0.188); median lipid layer 87 (IQR 77–90) and 86 (IQR 74–100) (nm, p  = 0.451); median meniscus height 0.22 (IQR 0.19-0,31) and 0.24 (IQR 0.20–0.27) (mm, p  = 0.862), median Meibomian gland atrophy 33 (IQR 24–45) and 31.5 (IQR 25–39) (%, p  = 0.524); and mean osmolarity 306.6 (SD ± 21.13) and 313.8 (SD ± 29) (mOsm, p  = 0.297). There was no statistically significant relationship between the repetitive use of 2% iodinated solution and signs or symptoms compatible with dry eye syndrome in this group of patients.

Conclusions

The findings suggest that 2% povidone iodine is a safe and efficacious agent for ocular surface antisepsis during intravitreal injections, not leading to substantial ocular surface modifications. This conclusion supports the continued use of povidone iodine in routine ophthalmic procedures without increased risk of inducing dry eye syndrome.

The use of povidone iodine (PVPI) for ocular surface asepsis is widespread, both for surgical procedures and intravitreal injections [ 1 , 2 , 3 , 4 , 5 ]. Surgeries for cataracts, glaucoma, and intravitreal injections have become common and frequent procedures in ophthalmology, leading to the serial exposure of patients’ eyes to iodine solutions [ 5 , 6 , 7 , 8 , 9 , 10 ]. These changes are directly associated with dry eye syndrome [ 11 , 12 ].

In particular, studies have demonstrated that intravitreal injections used to treat diabetic macular edema or age-related macular degeneration result in significant changes in the ocular surface, leading to dry eye syndrome and damage to homeostasis of the ocular surface [ 5 , 11 , 13 , 14 ].

Dry eye syndrome is a multifactorial disease of the ocular surface characterized by the loss of tear film homeostasis, hyperosmolarity, inflammation, damage and neurosensory abnormalities [ 11 , 15 , 16 , 17 , 18 ]. Its etiology is variable, ranging from nonspecific inflammation of the ocular surface to direct chemical or physical aggression, infections, and autoimmune diseases [ 11 , 12 , 15 , 19 ].

In addition to the most common symptoms, burning sensation, itching, speck, eye redness, excess tearing reflex, brightness sensitivity, and quality of vision loss are also frequent findings that affect efficiency at work and the quality of life of patients [ 11 , 12 , 15 , 19 , 20 ].

This study aimed to observe changes in the ocular surface and tear film due the serial use of 2% PVPI, the gold standard drug for asepsis of the ocular surface. As it is well known that pre-injection antisepsis of the ocular surface with PVPI has a toxic effect on the corneal epithelium, the aim is to identify changes in the tear film and ocular surface and avoid serious problem like dry eye syndrome [ 11 , 12 , 21 , 22 ].

A case-control study was conducted at the Ophthalmology and Psicology Clinic (APMTO MD) in Londrina, Paraná. The patients were recruited from the Retina and Vitreous Institute (AMBC MD) in Londrina, Paraná. The study included 34 individuals (68 eyes). 14 males, 20 females, aged 48 to 94 years. All participants signed the informed consent form, which allowed their participation in the study. Inclusion criteria were individuals who received application of 2% PVPI eyedrops for anti-VEGF IVIs treatment with the contralateral eye used as control, that had not been treated with any topical medication during the same period of applications and good comprehension of the Ocular Questionnaire Surface Disease Index (OSDI). Exclusion criteria were patients who could not understand the OSDI questionnaire; patients using antidepressant medicine, diuretics, sympathomimetics, eye drops for glaucoma, or eye lubricants; people with allergies to iodine; unfavorable clinical conditions to undergo the examination procedures for the study; inappropriate test quantity and quality; unsatisfactory images or unsatisfactory and inadequate data.

The study was approved by the Ethics and Research Committee Involving Human Beings of the State University of Londrina by N. 5.300.176.

The individuals underwent directed clinical and ophthalmological analysis, received explanations about the study, used their data, and signed consent forms. All clinical measures were performed using the IDRA equipment (SBSSISTEMI, Orbasano, Torino, Italy), at which time the OSDI questionnaire was also applied and tear osmolarity was collected using the I-PEN ® (I-MED PHARMA INC. Dollard-des-Ormeaux, QC, Canada). All examinations and administration of the questionnaire were performed by the same professional. No drops or medications that could cause changes in any subsequent measurements were used.

The variables analyzed were age, sex, date of the last PVPI application, number of PVPI applications, OSDI questionnaire, tear osmolarity, NBUT, tear film interferometry, tear meniscus height, percentage of meibomian gland loss, and blink quality. The sequence of procedures obeyed the following order: Explanation to the subject regarding the exams and questionnaire to which he would be submitted, guidance to the patient not to identify in any way the eye being treated and the eye not treated during data collection, nor during the questionnaire OSDI; patient positioning in the IDRA® equipment; capture of blinking quality video images; capture of tear film interferometry; capture of images to measure the height of the tear meniscus and immediate measurement; capture of tear film (NBUT); image capture for the percentage of meibomian gland loss by everting the lower eyelid with a cotton swab; positioning the patient outside the IDRA equipment; application of the I-PEN® electrode to capture tear osmolarity in the lower conjunctiva, first in the right eye, and subsequently in the left eye; application of the OSDI questionnaire.

All statistical analyses were performed using STATA® 18.0 Software and p-values ≤ 0.05 indicated statistical significance.

The Shapiro-Wilk test was used to verify data normality. Data that did not follow a normal distribution were analyzed using the Wilcoxon rank-sum test and were described as means and as medians and interquartile ranges. Data that showed normality were analyzed using the Student’s T test and presented as means and standard deviations. Descriptive, quantitative, and multivariate analyses compared treated (case) and untreated (control) eyes.

The average number of IVIs in treated eyes was 12 (range 6–20). The results in treated eyes compared with untreated eyes were respectively: median OSDI 16 (IQR 6–39) and 12.5 (IQR 8–39) ( p  = 0.380); mean NIBUT 10.30 (SD ± 2,62) and 10.78 (SD ± 2.92) ( s, p  = 0.476); median blinking quality 100 (IQR 100) and 100 (IQR 100 ) (%, p  = 0.188); median lipid layer 87 (IQR 77–90) and 86 (IQR 74–100) (nm, p  = 0.451); median meniscus height 0,22 (IQR 0.19–0.31) and 0.24 (IQR 0.20–0.27) (mm, p  = 0.862), median Meibomian gland athrophy 33 (IQR 24–45) and 31.5 (IQR 25–39) (%, p  = 0.524); and mean osmolarity 306.6 (SD ± 21.13) and 313.8 (SD ± 29) (mOsm, p  = 0.297).). The results revealed that the use of 2% PVPI did not affect the analyzed variables in a statistically significant way. All data is summarized on Table  1 .

These results are disposable on fig 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 and 9 as annexed.

Histogram showing the days of last application of IVIS ( intravitreal injections ) in treated eyes and the density showing the proportion of eyes in each period of time

Histogram showing the number of application ov IVIS ( intravitreal injections ) in treated eyes and the density showing the proportion of eyes in each amount of number of applications

Blue box plot showing score OSDI ( Ocular Surface Disease Index ) in treated eyes comparing with pink box plot showing score OSDI in fellow eyes

Blue box plot showing NIBUT ( non invasive break up time ) in seconds in treated eyes comparing with pink box plot showing NIBUT in seconds in fellow eyes

Blue box plot showing blink quality in treated eyes comparing with pink box plot showing blink quality in fellow eyes

Blue box plot showing lipid layer in treated eyes comparing with pink box plot showing lipid layer in fellow eyes

Blue box plot showing meniscus height in milimeters in treated eyes comparing with pink box plot showing meniscus height in milimeters in fellow eyes

Blue box plot showing Meibomian gland loss in treated eyes comparing with pink box plot showing Meibomian gland loss in fellow eyes

Blue box plot showing tear osmolarity in miliosmoles in treated eyes comparing with pink box plot showing osmolarity in miliosmoles in fellow eyes

Through multivariate analysis, we obtained some interesting outcomes as follows:

When controlling for NIBUT, meibomian gland atrophy, number of applications, and days of the last application according to treatment, sex was an important variable in explaining the variability in the OSDI score (coef = 15.63 | p-value = 0.003). On average, controlling for the abovementioned variables, being female contributed to an increase in the OSDI to 15.63 points.

After controlling for meniscus height and age according to treatment, tear osmolarity contributed significantly to variability in the lipid layer (coef = -0.266, p  = 0.004). In this sense, the addition of one unit in tear osmolarity led to a -0.266 drop in the lipid layer.

After controlling for meniscus height, OSDI, days since the last application, age, and sex according to the treatment, these factors contributed significantly to the variability in the lipid layer [(coef = 0.562 | p-value = 0.004) (coef = − 5.622 | p-value = 0.048)]. In this sense, the addition of one year of age led to a decrease of -0.562 on average. For the same treatment group, female sex led to a decrease of -5,622.

Age, lipid layer, meniscus height, sex according to treatment, age according to treatment, and sex were important factors for explaining the variability in tear osmolarity.

We noticed that a greater age correlated with lower tear osmolarity. However, being in the treated group reduced the decrease in tear osmolarity with advancing age.

Being female implied higher tear osmolarity. However, the increase in tear osmolarity was smaller in the treated group.

A greater height of the lipid layer and meniscus correlated with lower tear osmolarity.

The present study showed that the use of topical PVPI at 2% did not cause significant damage to the ocular surface when the findings of the ocular surface and tear film analyses were used.

Our results contradict some existing data indicating the toxicity of long-term iodine use on the ocular surface; we found two statistically relevant results that the application of iodine may improve the stability of the tear film in the elderly and women, since the eyes in older individuals and female patients that received iodine showed a smaller increase in tear osmolarity [ 4 , 14 , 23 , 24 ].

Moreover, the results of this study corroborated some hypotheses that the use of PVPI could be positive in some dry eye disease diagnostic features, such as the improvement of the tear film meniscus height and the decrease of the tear film osmolarity [ 25 , 26 ].

A localized anti-inflammatory surface effect of the anti-VEGF agent used in intravitreous injections should be considered and assessed in further studies [ 22 , 25 ].

The literature review also shows that there was an improvement in the tear function of some patients who used iodine in ocular asepsis [ 25 , 26 , 27 ], perhaps due to an antimicrobial action preventing the proliferation of bacterial flora that could produce harmful enzymes or cause meibomitis and blepharitis [ 25 , 26 , 28 ].

The cell regeneration mechanism might have satisfactorily recomposed the ocular surface or the tear homeostasis might have compensates for the damage caused by iodine in the cells in question; furthermore, these are just hypotheses.

We also determined that the risk factors for dry eye disease, age and female sex [ 10 , 16 , 29 , 30 ], were associated with the observed clinical data: greater ages lower the height of the tear meniscus, the greater the tear osmolarity, and the smaller the lipid layer of the tear film. The female sex was also associated with higher OSDI scores and fewer tear film lipid layers.

Regardless of the cause or consequence, the osmolarity and lipid layer of the tear film were inversely proportional.

Through multivariate analysis, we determined that the risk factors for dry eye syndrome, age, and female sex correlated with worse results in the tear meniscus measurement tests, OSDI questionnaire, and tear film interferometry, corroborating the literature implicating them as risk factors for dry eye disease [ 20 , 30 , 31 ].

Moreover, due to the sample size, false negatives, or simply because in practice, iodine in the amount and frequency used does not lead to histological damage that may reflect functional changes. The results did not discourage the use of iodine for ocular asepsis but also did not indicate its use for protocols with higher concentrations or more applications than those used in current protocols.

The strengths of the study are as follows: the same patient was the control and treated group, avoiding any environmental or medical bias. The number of injections administered was higher than that reported in other studies. No drops were used during the examination to avoid artificial changes to the tear film.

The limitations of this study were as follows: the study had a small sample size of 34 patients, resulting in 68 eyes being analyzed, which may have caused an analysis bias when using these data in the general population. We must remember that the analyzed population was from southern Brazil and had mostly descended from Italian, German, Spanish, and Portuguese immigrants; therefore, these data may only reflect the specific epidemiology of this population. The meibomian glands analyzed were located in the inferior tarsus.

The use of iodine on the ocular surface was not significantly associated with any of the evaluated parameters. There were no statistically significant correlations between the tests applied to the case eyes. The current study indicates that the application of 2% topical povidone-iodine (PVPI) does not inflict significant damage to the ocular surface, as evidenced by the analyses of the ocular surface and tear film. Notable strengths of this study include the use of the same patient as both the control and the treated subject, which minimizes potential biases from environmental or medical factors. Additionally, the absence of any artificial agents during the examination ensures that the tear film remains unaltered.

Contrary to previous concerns regarding the long-term toxicity of iodine on the ocular surface, our findings suggest potential benefits of iodine application in stabilizing the tear film, particularly in older individuals and female patients. This is supported by a smaller increase in tear osmolarity in these groups following iodine application. Furthermore, the study corroborates hypotheses that PVPI may positively affect certain Dry Eye Disease diagnostic features, such as improved tear film meniscus height and reduced tear film osmolarity.

Data availability

No datasets were generated or analysed during the current study.

Abbreviations

Povidine or polyvinylpyrrolidone-iodine

• Intravitreal injections

Vascular endothelial growth factor

Ocular Surface Disease Index

Non invasive break up time

Blink quality

Lipid layer

Standard deviation

Interquartile range

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Acknowledgements

APMO provided IDRA analysis, and was a contributor to design the study, revised, written and approved the manuscript. AMBC Applied intravitreal injections and provided patients for the study and was a contributor to design the study, revised, written and approved the manuscript.

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José Henrique Casemiro

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Ana Paula Miyagusko Taba Oguido

Londrina State University, Avenida Robert Koch, 60, Londrina, Paraná, 86038-440, Brazil

Antonio Marcelo Barbante Casella

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JHC analyzed and interpreted patient data, reviewed the literature and was a major contributor to the acquisition of data, interviewed the patients, sponsored supplies, designed the study and written the manuscript. APMO provided IDRA analysis, and was a contributor to design the study, revised, written and approved the manuscript. AMBC Applied intravitreal injections and provided patients for the study and was a contributor to design the study, revised, written and approved the manuscript.

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Casemiro, J.H., Oguido, A.P.M.T. & Casella, A.M.B. Using 2% PVPI topical solution for serial intravitreous injections and ocular surface findings: a case control study. Int J Retin Vitr 10 , 41 (2024). https://doi.org/10.1186/s40942-024-00557-1

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Received : 11 March 2024

Accepted : 07 May 2024

Published : 29 May 2024

DOI : https://doi.org/10.1186/s40942-024-00557-1

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