Prevalence and characteristics of patients with severe mental illness and borderline intellectual functioning - Report from the UK700 randomised controlled trial of case management

Background Low cognitive ability and developmental delays have been implica ted in the causation of mental illness. Aims To examine the prevalence, socio-demographic characteristics, psychopa thology and social functioning profiles of people with low intelligence and recurrent psychotic illness. Method A multi-centre randomised controlled trial of case management provid ed the opportunity to explore associations between mental illness and borde rline intellectual functioning (assessed using the National Adult Reading T est). Results Overall prevalence of borderline intelligence was 18%. Significant positive associations were shown with: being Black Caribbean; having a fath er who worked in a manual occupation; lower educational achievement; having had special education; longer course of illness. Those with borderline int elligence had greater disability and were more likely to suffer extrapyrami dal side-effects and show evidence of negative symptoms. Educational achiev ement, history of special education and social class were-the best socio-de mographic predictors of intellectual level. Conclusions Many patients who attend generic psychiatric services have cons iderable intellectual deficits. This may lead to difficulties in other doma ins of adaptive functioning, and merits further investigation as well as cl inical vigilance. Declaration of interest Funded in part by the Department of Health.