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December 8, 2021

Potential Lessons for DSM From Contemporary Philosophy of Science

Author Affiliations
  • 1Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University, Richmond
  • 2Department of Psychiatry, Virginia Commonwealth University, Richmond
JAMA Psychiatry. 2022;79(2):99-100. doi:10.1001/jamapsychiatry.2021.3559

This Viewpoint seeks to examine current psychiatric nosology through the lens of modern philosophy of science.1 Elsewhere I have strongly defended, in both philosophical and moral terms, the reality of major mental illness as an aggregate category.2 However, the status of our current nosologic categories is much less clear. Many scientific theories assume constructs that are not directly observable (muons, genetic drift) but whose existence is inferred. In mental health research, psychiatric diagnoses play such a role. We assume that constructs, such as schizophrenia or alcohol use disorder, exist but we can only observe the signs, symptoms, and course of illness that we postulate result from these disorders. Despite years of research, we cannot explain or directly observe the pathophysiologies of major mental health disorders that we could use to define essential features.

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    2 Comments for this article
    Are psychiatric diagnoses pragmatic symptom clusters or (nearly) natural kinds?
    Lynn Waterhouse, PhD | The College of New Jersey
    Recently Kendler (2021) published an opinion in JAMA Psychiatry, “Viewpoint: Potential Lessons for DSM From Contemporary Philosophy of Science.” He argued that researchers should take an instrumentalist approach to psychiatric diagnoses rather than an approach based in scientific realism. Scientific realism is the belief that establishing natural kinds is the goal of science. Natural kinds are thought to identify underlying biological or physical entities. Scientific realism values natural kinds such as DNA structure, because they lead to the discovery of other natural kinds, genes, that yield life-altering knowledge. Instrumentalism, by contrast, argues that natural kinds—DNA structure, genes, the speed of light, neurons—are no more valuable than pragmatic descriptions, because all science findings are no more than temporary pragmatic descriptions.

    At present, many clinicians and researchers take a mixed view. They believe that psychiatric diagnoses are likely to be biological entities (natural kinds), but that diagnoses can best be understood as pragmatic descriptions of prototypical clusters of symptoms.1,2 A minority of clinicians and researchers are scientific realists who believe that pragmatic psychiatric categories impede the discovery of natural kinds of pathophysiologies.3,4

    Kendler (2021) offers five arguments in favor of instrumentalism. First, the pessimistic induction theory of psychiatric diagnoses holds that category replacements, such as autism replacing childhood schizophrenia, demonstrate that no diagnoses can ever be natural kinds. Second, because the DSM is based on pragmatic symptom clusters and not natural kinds of pathophysiologies, finding natural kinds is not necessary. Third, psychiatric categories cannot be tested for validity because there is not enough evidence to decide between competing diagnostic formulations. Therefore, pragmatic symptom clusters are the best we can do for now. Fifth, an instrumentalist view of psychiatric categories can tamp down the reification of diagnoses that are, in fact, pro tem hypotheses.

    Unlike the five reasons Kendler (2021) offers for the value of instrumentalism, there is only one core argument for scientific realism in psychiatry: “nosology is a blindfold.”3,4 Scientific realism argues that natural kinds of pathophysiologies cannot be discovered while DSM categories are the basis for research.3,4 Psychiatric categories are refined by ignoring heterogeneity, but symptoms that don’t fit within a diagnosis are real, and unresolved heterogeneity is meaningful.3 It is exactly the ignored heterogeneity that must be included for study rather than being refined away. This ignored heterogeneity can only be explained when research ignores DSM categories.

    1. Kendler KS. Potential Lessons for DSM From Contemporary Philosophy of Science. [published online December 8, 2021]. JAMA Psychiatry. doi:10.1001/jamapsychiatry.2021.2877

    2. Tsou JY. Natural kinds, psychiatric classification and the history of the DSM. History of Psychiatry. 2016;27(4):406–424.

    3. Waterhouse L. Is autism a unitary biological entity? A revised and extended response to “A radical change in our autism research strategy is needed: Back to prototypes” Autism Research. 2021;14(10):2241-2242.

    4. Hyman SE. Psychiatric Disorders: Grounded in Human Biology but Not Natural Kinds. Perspectives in Biology and Medicine. 2021;64(1):6-28.
    Applying philosophy of science to psychiatry.
    Niall McLaren, MBBS FRANZCP | Retired
    In a commentary on the current unsatisfactory state of psychiatric nosology [1], Kendler suggested we could learn from the philosophy of science. He believes mental disorder are real and of essentially the same nature as “classical physical‐medical disorders,” thus explicable in biological terms [2]. Psychiatry, he avers is “a legitimate biomedical discipline,” its scientific status not in doubt, but psychiatric disorders are “probably inherently multifactorial” which creates enormous problems in understanding “the pathophysiologies of major mental health disorders.” Thus, “… it is very unlikely that we now possess definitive theories of their etiology.” He is, however, optimistic, not least because “the scientific method itself provides scientists with an epistemic privilege.”

    Indubitably, psychiatric nosology is a weakness but I believe his optimism is misplaced, and his commentary shows why. It is true that scientists have an epistemic advantage but, prior to that, they have the overwhelming epistemic duty to examine crtically the basic premises of their programs. The first question any seientist must answer is this: Is what we are doing a legitimate endeavor? So Kendler's research program must starts here: Can mental disorder be understood in biological terms? Kendler leaves no doubt that throughout his career, he has believed the answer to this question is an emphatic Yes. But he and his many supporters have assumed this, they have never proven it.

    Some years ago, I showed that no psychiatrist, or philosopher or neuroscientist, had ever assembled anything that amounts to a valid reductionist (physicalist) model of mental disorder [3]. Thus, biological psychiatry meets criteria as an ideology, not a science. In an exhaustive analysis, philosopher Daniel Stoljar [4] concluded that there is no version of physicalism that is both informative and true. It is either truism, or it is false.

    My case is that the entire biological project in psychiatry is misconceived. It can never provide a full, explanatory account of mental disorder. Adopting a critical view of the ontological claims of biological psychiatry quickly leads to an alternative working model [5]. Kendler needs to show that his fundamental ontological beliefs are valid, that biology can explain mental life, including mental disorder, while purely psychological factors cannot. As he has no valid model of mind beyond his unexamined commitment to biological reductionism, I don't believe he can. He can't just choose from philosophy those bits that suit his case, and ignore the more important parts that don't.

    1. Kendler K (2021).Potential Lessons for DSM From Contemporary Philosophy of Science
    JAMA Psychiatry doi:10.1001/jamapsychiatry.2021.3559
    2. Kendler K (2016). The nature of psychiatric disorders. World Psychiatry. 2016 Feb; 15(1): 5–12. doi:  10.1002/wps.20292
    3. McLaren N (2013). Psychiatry as Ideology. Ethical Human Psychology and Psychiatry 15: 7-18.
    4. Stoljar D (2010). Physicalism. Oxford: Routledge.
    5. McLaren N (2021): Natural Dualism and Mental Disorder: The biocognitive model for psychiatry. London: Routledge.