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I EXPLAINING DEPRESSION EXPLAINING DEPRESSION: A DISCOURSE ANALYSIS OF FAMILY PHYSICIANS’ AND NEUROSCIENTISTS’ ACCOUNTS OF EXPLANATORY MODELS AND THE CHEMICAL IMBALANCE HYPOTHESIS OF DEPRESSION A Thesis Submitted to the College of Graduate and Postdoctoral Studies In Partial Fulfillment of the Requirements For the Degree of Doctor of Philosophy In the Department of Psychology University of Saskatchewan Saskatoon By Kristjan J. Sigurdson Copyright Kristjan J. Sigurdson, July 2019. All rights reserved i Permission to Use In presenting this thesis/dissertation in partial fulfillment of the requirements for a Postgraduate degree from the University of Saskatchewan, I agree that the Libraries of this University may make it freely available for inspection. I further agree that permission for copying of this thesis/dissertation in any manner, in whole or in part, for scholarly purposes may be granted by the professor or professors who supervised my thesis/dissertation work or, in their absence, by the Head of the Department or the Dean of the College in which my thesis work was done. It is understood that any copying or publication or use of this thesis/dissertation or parts thereof for financial gain shall not be allowed without my written permission. It is also understood that due recognition shall be given to me and to the University of Saskatchewan in any scholarly use which may be made of any material in my thesis/dissertation. Requests for permission to copy or to make other uses of materials in this thesis/dissertation in whole or part should be addressed to: Head of Department Department of Psychology University of Saskatchewan 154 Arts Building, 9 Campus Drive Saskatoon, Saskatchewan, S7N 5A5, Canada OR Dean College of Graduate and Postdoctoral Studies University of Saskatchewan 116 Thorvaldson Building, 110 Science Place Saskatoon, Saskatchewan, S7N 5C9, Canada i Abstract The etiological explanations for depression, along with the received views of the way the brain and body function, have shifted from an excess of black bile to impaired neuroplasticity and neuroimmune functions. A common biological explanation for depression is the chemical imbalance hypothesis, which posits that depression is caused by a deficiency of monoamines, particularly serotonin, in the depressed person’s brain. Many scholars have argued that the chemical imbalance hypothesis is unable to adequately explain depression and antidepressant treatment. However, while the etiological understanding of depression is complex and incomplete, the chemical imbalance hypothesis remains pervasive and persuasive among laypersons and clinicians. I begin this dissertation with an introduction to biological psychiatry and neuroscience. The dissertation includes a brief history of Western/English approaches to the diagnosis and etiology of depression, a chapter on my ontological, epistemological, and methodological assumptions, two manuscript-style research studies, and concludes with a general discussion. In the two studies, I demonstrate how a sample of family physicians and neuroscientists accounted for using the chemical imbalance hypothesis of depression and other explanations of depression, the persuasive rhetorical features in their arguments, and the functions achieved by these accounts. In study 1, I analyzed an interview data set with 11 family physicians. Using a discursive analytic approach, I argue that these physicians are utilizing the chemical imbalance hypothesis as a persuasive rhetorical device to motivate patients toward treatment, to attempt to minimize self-blame and stigma, to instill hope and confidence in the treatment, and to contribute generally to scientific knowledge among patients. In the discussion I provide a critique of the general assumptions upon which their arguments rely. For study 2, I interviewed 10 neuroscientists who conduct depression research. Using a discursive analytic approach, I present how a sample of neuroscientists working on a biological understanding of depression argue for and/or against the chemical imbalance hypothesis of depression. I argue that they maintain support for the chemical imbalance hypothesis through the construction of depression as a brain-based disorder and the brain as functioning through chemical transmissions, and that they argue against the chemical imbalance hypothesis by defining this hypothesis as a specific deficiency of serotonin and drawing attention to the failings and shortcomings of the hypothesis. I argue that their rhetorical construction of a distinction between a general chemical imbalance and a specific serotonin deficiency allows for the maintenance and support of the fundamental assumption that depression is a brain-based disorder, while simultaneously denying that depression is exclusively a problem with the serotonin system. I discuss alternative explanations of depression proposed by the scientists and show how they construct the serotonin hypothesis as a persuasive rhetorical device resistant to replacement. The results of studies 1 and 2 suggest that the chemical imbalance hypothesis of depression, while limited in its specific form to explain the cause of depression, has value and merit in scientific and lay discourses. In the general discussion, I summarize the arguments for and against the chemical imbalance hypothesis and suggest ways that the general chemical imbalance explanation can be augmented with additional ideas from contemporary neuroscience. I discuss the discipline of translational neuroscience, which aims to bridge the gap between science and practice, and provide commentary using extracts from the interviews. I conclude with a reflexive examination of my position. ii Acknowledgements First and foremost, I want to thank my research supervisor, Dr. Linda McMullen, for her warm and wise mentorship throughout the program. You provided support, guidance, and inspiration that has been invaluable for both research and life. Thank you to my advisory committee members, Dr. Erika Dyck, Dr. John Howland, and Dr. Ulrich Teucher, for your thoughtful critique, encouragement, and patience. Your unique perspectives toward this topic expanded my view and contributed immensely to the final product. Thank you to my external examiner, Dr. Kieran O’Doherty, for your challenging questions and valuable feedback. To the qualitative research team members, thank you for your contributions to my knowledge of qualitative research and discourses, and my analysis of the data. Thank you to the physicians and scientists who volunteered their time to participate in this research. Last but not least, thank you to my family for your support and encouragement throughout this process. iii Table of Contents Permission to Use.................................................................................................................................... i Abstract .................................................................................................................................................... ii Acknowledgements ............................................................................................................................. iii Table of Contents .................................................................................................................................. iv Chapter One: Introduction ................................................................................................................. 1 1.1 Outline ........................................................................................................................................................... 1 1.2 Neuroscience, Psychiatry, and the Study of Depression .............................................................. 1 1.3 References .................................................................................................................................................... 4 Chapter Two: The Diagnosis and Etiology of Depression in Canada and the United States of America ................................................................................................................................... 6 2.1 The Diagnosis of Depression ................................................................................................................. 6 2.1.1 DSM-5 controversy. ........................................................................................................................................... 6 2.2 Biologically-Based Etiologies of Depression.................................................................................... 7 2.2.1 Humoral explanations. ..................................................................................................................................... 8 2.2.2 Mechanical explanations. ................................................................................................................................ 9 2.2.3 Influence of antidepressants. ........................................................................................................................ 9 2.2.4 The monoamine hypothesis. ....................................................................................................................... 11 2.2.5 The amine-receptor hypothesis. ................................................................................................................ 14 2.2.6 Genetics and heritability hypotheses. ..................................................................................................... 14 2.2.7 The neuroendocrine
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