Extensive and diverse conceptual work towards developing a definition of 'mental disorder' was motivated by the declassification of homosexuality from the Diagnostic and Statistical Manual in 1973. This highly politicised event was understood as a call for psychiatry to provide assurances against further misclassification on the basis of discrimination or sociopolitical deviance. Today, if a definition of mental disorder fails to exclude homosexuality, then it fails to provide this safeguard against potential abuses and therefore fails to do an important part of the work it was intended to do. We argue that fact-based definitions of mental disorder, relying on scientific theory, fail to offer a robust definition of mental disorder that excludes homosexuality. Definitions of mental disorder based on values do not fare better: these definitions are silent on questions about the diagnostic status of individuals in oppressive societies and over-inclusive of mental or behavioural states that happen to be negatively valued in the individual's social context. We consider the latest definition proposed for the Diagnostic and Statistical Manual-5 (DSM-5) in light of these observations. We argue that definition fails to improve on these earlier deficiencies. Its inclusion in the manual may offer false reassurance against repetition of past misclassifications. We conclude with a provocation that if candidate definitions of mental disorder are unable to exclude homosexuality, it might perhaps be preferable not to attempt a definition at all.
