Prevalence of psychiatric symptoms in adults with mental retardation and challenging behaviour.

The relation between psychiatric symptoms and different types of challenging behaviour in adults with mental retardation was investigated, using an instrument designed for use by non-specialist informants. A sample of 165 persons with mental retardation was surveyed for the presence of psychiatric symptoms, level of mental retardation, and self-injurious and other types of challenging behaviour. Challenging behaviour was associated with increased prevalence of psychiatric symptoms, especially anxiety and psychosis, less with hypomania, and not with depression. No association between anxiety and self-injurious behaviour was found. An association between psychiatric symptoms and challenging behaviour on a group level is an initial step towards understanding causes of challenging behaviour. Issues remain, like how causation takes place on an individual level, and the nature of psychiatric disorders in persons with severe and profound mental retardation.