Psychiatric disorders and behavior problems in people with intellectual disability.

The relationship between behavior problems and psychiatric disorders in individuals with intellectual disability is still unresolved. The present study compares the prevalence and pattern of psychiatric disorders in individuals with intellectual disability who were assessed on the ABC to have moderate and severe behavior problems and a matched group of individuals without such problems. Both groups were living in community settings and had their intellectual disability varied from mild to profound degrees. The participants were screened for psychiatric disorders using four different instruments; the Reiss Screen, the Mini PAS-ADD, the DASH-II and the ADD. The group with moderate and severe behavior problems showed significantly more symptoms of psychiatric disorders than the group without such problems when items related to behavior disorders were omitted, and the majority of the participants with behavior problems had symptoms of the main psychiatric disorders. The participants with mild and moderate intellectual disability showed more symptoms of psychosis and depression than the participants with severe and profound intellectual disability. There were no direct associations between individual behavior problems and psychiatric disorders, but the group with mild/moderate intellectual disability showed a somewhat different pattern of associations than the group with severe/profound intellectual disability. Depression was associated with screaming and aggression in the participants with severe and profound intellectual disability, and with self-injury in the participants with mild and moderate intellectual disability. The finding that the majority of the participants with behavior problems showed symptoms of psychiatric disorders suggests that many behavior problems may be (unconventional) symptoms of psychiatric disorders or reflect a difficult life situation caused by a psychiatric disorders, or that a difficult life situation may contribute to both psychiatric disorders and behavior problems in individuals with intellectual disability.