The functions of psychiatric diagnosis

Psychiatric diagnoses are ubiquitous, but historically have been seen as problematic, even contested, categories. Calls for new models of mental distress have originated from psychiatry, clinical psychology, and the service user movement. However these proposals are limited in their scope. Taking a social constructionist critical realist epistemological approach, the thesis framed psychiatric diagnoses as active categories; constructed to meet particular needs and functions. The central research question of the thesis was to explore, from multiple perspectives, the functions of psychiatric diagnosis. Theoretical questions addressed the conceptual underpinnings of diagnostic categories, how they are used in practice, and their implications. Three methodologies were used. A textual examination of chapters of the DSM-5 analysed the heterogeneity across diagnostic criteria and explored diagnostic classification as a protocol for practice. Semi-structured interviews with clinicians (GPs, psychiatrists, clinical psychologists) and individuals who had received psychiatric diagnoses were used to examine the practices of diagnosis within and beyond the clinic. Finally, Freedom of Information Act requests made to NHS mental health trusts in the north of England were used to explore the uses of diagnosis in service entry and eligibility criteria. The findings revealed that psychiatric diagnoses performed multiple clinical, social, and administrative functions in multiple contexts, and acted as a proxy for various factors, with tensions arising across these functions. These functions invoked different underpinning conceptualisations, which were inconsistent across contexts. Diagnostic practices were found to be often at odds with the use prescribed by diagnostic manuals. Although clinicians used diagnosis as a flexible tool, categories were reified beyond the clinic with important implications for those diagnosed. The thesis structure reflects the tensions that arose as a result of these multiple functions, through a process of diagnostic categories travelling from the text of the classification itself, to clinicians, services, and beyond the clinic to the individuals who received them. These multiple uses and changing conceptualisations meant that the utility of one function could result in harmful costs elsewhere. At the intersection of these functions were the people diagnosed, for whom diagnostic categories had potentially damaging consequences. Diagnosis-focused clinicians and administrative structures such as benefits payments placed limitations on the extent to which individuals could publicly reject their diagnosis should they choose to. In contrast with previous proposals focused on replacing specific aspects of psychiatric diagnosis (such as taxonomy or individual assessment), a broader programme of system reform is advocated. Recommendations include the use of psychosocial and descriptive codes of the International Classification of Diseases and competency-based services