The semi-structured interview format followed by the psychiatrists was comprehensive and in keeping with best practice; more detailed information on such assessments of mental ill-health in persons with severe and profound intellectual disabilities has been reported elsewhere (Cooper, 2003). The assessment included at least one face-to-face meeting with the person with intellectual disabilities, and also with the person’s main carer. If the latter was a paid carer, parents or other close relatives were also interviewed if available. Information was sought from additional paid carers as required: typically this depended upon the length of time the main paid carer had known the person and the level of detail of current and background information known to that carer. Previous and current case notes were also reviewed by the psychiatrists. The first appointment was scheduled for a 1.5 h duration, and subsequent appointments arranged as required until all necessary information had been collected about current psychopathology, its severity and duration, and differentiation between longstanding characteristics and symptoms of mental ill-health, rated within the context of the person’s overall developmental level, using the rating scales. Information was also collected on the participant’s past psychiatric history, previous and current medical history, current and previous drug use and mental health interventions, past and current medical and psychiatric history of family members, personal background, social circumstances and social networks, developmental history and current developmental level, and personality development. A mental state examination was conducted. Physical health had already been assessed. The information from the sources was integrated, clinical diagnoses were determined by consultant psychiatrists specialised in working with adults with intellectual disabilities, and psychopathology was classified using the three diagnostic classificatory systems.