Dual diagnosis in offenders with intellectual disability: setting research priorities: a review of research findings concerning psychiatric disorder (excluding personality disorder) among offenders with intellectual disability.

Studies of so-called 'dual diagnosis', i.e. intellectual disability (ID) with an additional psychiatric disorder, are reviewed with particular reference to offending behaviour. Because of the paucity of studies of psychopathology in offenders with ID, the present paper opens with studies of broader issues of psychopathology among people with ID, notably those with depression, schizophrenia, mild depressive disorder, other major psychotic disorders, anxiety/neurotic disorder, autistic spectrum disorders and attention deficit hyperactivity disorder. There follows a review of the most established and commonly used measurement scales for dual diagnosis in ID. The review then focuses directly on those studies which have looked at the issues of dual diagnosis among offenders with ID. In keeping with other reviews in this series, the latter studies are classified according to the same criteria. Based on this review, it is apparent that there are high-priority research questions which concern the extent and nature of psychopathology among offenders with ID, most notably those with autistic spectrum disorders.