Do Psychiatric Diagnoses Explain? a Philosophical Investigation, Submitted By
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Do Psychiatric Diagnoses Explain? A Philosophical Investigation by Hane Htut Maung MA (Cantab), MB BChir, MPhil, MRCPsych Submitted for the Degree of Doctor of Philosophy December 2016 1 Abstract Do Psychiatric Diagnoses Explain? A Philosophical Investigation, submitted by Hane Htut Maung for the degree of Doctor of Philosophy, December 2016 This thesis is a philosophical examination of the explanatory roles of diagnoses in psychiatry. In medicine, diagnoses normally serve as causal explanations of patients’ symptoms. Given that psychiatry is a discipline whose practice is shaped by medical traditions, it is often implied that its diagnoses also serve such explanatory functions. This is evident in clinical texts that portray psychiatric diagnoses as referring to diseases that cause symptoms. However, there are problems which cast doubt on whether such portrayals are justified. I address these problems and examine whether psychiatric diagnoses provide explanations of symptoms. The first problem is conceptual. In diagnostic manuals, psychiatric diagnoses are defined by their symptoms. This suggests that invoking them as explanations of the symptoms amounts to circularity. I argue that this can be resolved with an appropriate conceptual framework that captures the complex semantic values of diagnostic terms and their different uses in clinical discourse. I put forward such a framework based on two-dimensional semantics. The second problem is ontological. Empirical research suggests that diagnostic categories in psychiatry do not correspond to invariant causal types, but are associated with variable combinations of diverse causes that interact across biological, psychological, and social levels. Given this heterogeneity, I argue that psychiatric diagnoses fall short of paradigmatic cases of causal explanation, but that some can still provide other sorts of useful causal explanatory information. The original contribution of this thesis is the illumination of the conceptual relations between diagnoses and symptoms. This philosophical work is important, because it can be brought to valuable application in modifying psychiatric practice. 2 Acknowledgments I would like to express my gratitude to the many people who greatly helped me in completing this thesis. Most of all, I would like to thank my supervisors, Rachel Cooper and Brian Garvey. Their guidance, support, and criticism were invaluable in motivating and shaping the thesis. Thanks also go to my examiners, Stephen Wilkinson and Alexander Bird, for taking the care to study my thesis and for engaging in a thoroughly stimulating dialogue during my viva voce examination. I greatly benefited from discussions with a number of colleagues in philosophy, to whom I am very grateful. These are Sam Fellowes, Dan Degerman, Moujan Mirdamadi, Faye Tucker, and Tomasz Herok. I would also like to thank my former colleagues in psychiatry, Neil Hunt, Gaetano Dell’Erba, and Dane Rayment, for helping me attain the clinical knowledge that was indispensable for this project. Special thanks go to Elizabeth Fistein, Tony Hope, and Werdie van Staden for encouraging my decision to enter academic philosophy of psychiatry. I am grateful for the financial support that enabled me to undertake this project. Funding for the project was provided by the Wellcome Trust (grant number 104897/Z/14/Z). I am also grateful for the supportive environment provided by Lancaster University’s Department of Politics, Philosophy, and Religion. Parts of this thesis have been published as peer-reviewed journal articles. A version of Chapter 3 has been published in Theoretical Medicine and Bioethics, and versions of Chapter 4 and Chapter 6 have been published in Studies in History and Philosophy of Biological and Biomedical Sciences. I am grateful to the journal editors and reviewers who offered useful comments on the manuscripts. Finally, I would like to thank my wife Shuna Gould and our son Theo for their love, support, and patience that made the completion of this thesis possible. 3 Declaration I hereby declare that this thesis is of my own composition and that it contains no material previously submitted for any other degree of qualification. The work in this thesis has been produced by me, except where due acknowledgement is made in the text. I confirm that this thesis does not exceed the prescribed limit of 80,000 words, including the main text and any footnotes but excluding the bibliography. Hane Maung 4 Publications from this Thesis A version of Chapter 3 has been published as: Maung, H. H. (2016b). “The Causal Explanatory Functions of Medical Diagnoses”. Theoretical Medicine and Bioethics. Published online first 16th September 2016. DOI: 10.1007/s11017-016-9377-5. A version of Chapter 4 has been published as: Maung, H. H. (2016c). “To What Do Psychiatric Diagnoses Refer? A Two-Dimensional Semantic Analysis of Diagnostic Terms”. Studies in History and Philosophy of Biological and Biomedical Sciences, 55: 1–10. A version of Chapter 6 has been published as: Maung, H. H. (2016a). “Diagnosis and Causal Explanation in Psychiatry”. Studies in History and Philosophy of Biological and Biomedical Sciences, 60: 15–24. 5 Contents Abstract ..................................................................................................................... 2 Acknowledgments ..................................................................................................... 3 Declaration ................................................................................................................ 4 Publications from this Thesis ................................................................................... 5 1. Introduction ......................................................................................................... 10 1.1 The problem ....................................................................................................................... 10 1.1.1 Overview ...................................................................................................................... 10 1.1.2 The conceptual problem ............................................................................................ 14 1.1.3 The ontological problem ........................................................................................... 21 1.2 Significance of the research .............................................................................................. 23 1.2.1 Importance of the problem ....................................................................................... 23 1.2.2 Positioning of the research ........................................................................................ 27 1.2.3 Scope of this thesis ..................................................................................................... 30 1.3 Synopsis ............................................................................................................................... 33 2. The Functions of Diagnoses ............................................................................... 39 2.1 Introduction ........................................................................................................................ 39 2.2 The various functions of diagnoses ................................................................................ 40 2.2.1 Hypothesis ................................................................................................................... 40 2.2.2 Explanation ................................................................................................................. 42 2.2.3 Prediction ..................................................................................................................... 43 2.2.4 Intervention ................................................................................................................. 44 2.2.5 Denotation ................................................................................................................... 45 2.2.6 Classification ............................................................................................................... 45 2.2.7 Normative .................................................................................................................... 47 2.2.8 Semiotic ........................................................................................................................ 48 2.2.9 Social ............................................................................................................................. 49 2.3 When diagnoses fail to explain ........................................................................................ 51 2.3.1 The importance of the explanatory function.......................................................... 51 2.3.2 Medically unexplained syndromes ............................................................................ 56 2.3.3 Problems with psychiatric diagnoses ....................................................................... 60 2.4 Conclusion .......................................................................................................................... 64 6 3. Medical Diagnoses as Causal Explanations ....................................................... 66 3.1 Introduction ........................................................................................................................ 66 3.2 The explanandum ................................................................................................................