Descriptive diagnosis, personality disorder and detention

By contributing to the detention of people who could not otherwise be detained, psychiatric diagnoses differ from diagnoses elsewhere in medicine. Legal changes in the US and draft legislation in the UK extend the role that the diagnosis of personality disorder plays in authorising detention. This paper examines the degree to which the diagnosis is valid for purposes beyond description. The criterion most frequently invoked to demonstrate that psychiatric diagnoses are valid for purposes other than description is dysfunction. Two aspects of the personality disorders have limited the ability of dysfunction to distinguish normal from abnormal personalities. These are the relative temporal stability of a sufferer's level of function and the absence of characteristic patterns of dysfunction associated with particular symptoms and signs. Continued efforts to improve the validity and reliability of diagnostic categories should be accompanied by explicit descriptions of the uses for which those categories are valid. Appropriate structuring of legislation can minimise the difficulties that attend the use of systems of classification in settings for which they were not designed.