The conceptual evolution of exclusion rules in the DSM: Problems with determining when one diagnosis should rule out...

For each mental disorder listed in the Diagnostic and Statistical Manual of Mental Disorders (DSM), the classification provides diagnostic criteria which list the symptoms required for diagnosis. Most sets of diagnostic criteria incorporate exclusion criteria, which state that a diagnosis can only be made in the absence of certain other diagnoses (for example, a specific learning disorder can usually only be diagnosed in the absence of intellectual disability). Exclusion criteria make it clear whether diagnoses can be made together or are exclusive. In the absence of such guidelines, diagnoses will not be reliable and the prevalence of conditions cannot be measured. Through tracing the conceptualisation of exclusion criteria across the DSM series, I show that exclusion criteria are necessary, but that determining what they should be has been intractably difficult. The exclusion rules employed by a classification reflect basic ontological and theoretical judgements about the causal structure of psychopathology. Pragmatic judgements also often play a role. As such, exclusion criteria introduce multiple tensions into the DSM system. On the one hand, exclusion criteria are required. On the other hand, the fact that exclusion criteria often rely on theoretical suppositions undermines any claims that the DSM can avoid controversial commitments. At the same time, the role played by pragmatic concerns, which are by nature often context dependent, threatens the employment of the DSM as a multi-purpose classification used world-wide. More fundamentally, difficulties around determining exclusion rules can arise because it is often unclear how mental disorders might be individuated, and such difficulties undermine hopes that the DSM might describe 'natural kinds' of disorder.