The distinction between personality disorder and mental illness

BACKGROUND: Proposals by the UK Government for preventive detention of people with 'dangerous severe personality disorders' highlight the unresolved issue of whether personality disorders should be regarded as mental illnesses. AIMS: To clarify the issue by examining the concepts of psychopathy and personality disorder, the attitudes of contemporary British psychiatrists to personality disorders, and the meaning of the terms 'mental illness' and 'mental disorder'. METHOD: The literature on personality disorder is assessed in the context of four contrasting concepts of illness or disease. RESULTS: Whichever of the four concepts or definitions is chosen, it is impossible to conclude with confidence that personality disorders are, or are not, mental illnesses; there are ambiguities in the definitions and basic information about personality disorders is lacking. CONCLUSIONS: The historical reasons for regarding personality disorders as fundamentally different from mental illnesses are being undermined by both clinical and genetic evidence. Effective treatments for personality disorders would probably have a decisive influence on psychiatrists' attitudes.