Developmental level and other factors associated with symptoms of mental disorders and problem behaviour in adults with intellectual disabilities living in the community

Background Studies of the relationship between the level of intellectual disability and mental and behavioural disorders have reported divergent findings regarding the direction of the relationship and how it is related to different mental disorders. Aims To investigate the relationship between levels of intellectual disability and mental disorders and problem behaviour after adjusting for other relevant factors: age, gender, autism, genetic syndromes, the neurological conditions cerebral palsy and epilepsy, negative life events and quality of the social care provided. Methods A community sample of adults with intellectual disabilities (N = 593) were assessed using the Psychopathology Checklists for Adults with Intellectual Disability. A hierarchical regression model with forced entry was employed. Results Both linear and curvilinear relationships between intellectual disability and mental disorders were found after controlling for relevant factors that was independently associated with specific mental disorders. Conclusions Psychopathology models for adults with intellectual disabilities should include the level of intellectual disability, either in a linear or a non-linear way. Future research on this issue should focus on people with borderline intellectual disability