The extent to which mental disorder and learning disability co-occur varies substantially between studies. This review set out to identify studies in children and/or adolescents with acceptably rigorous methods and to ascertain key risk factors.

The review found nine studies with acceptable methods, 4 which compared prevalence of mental disorder in populations of those with and without learning disability, and 5 studies estimated rates of mental disorder in those with learning disability.

The studies demonstrate rates of co-morbidity for children and adolescents between 30 and 50% with a relative risk of mental disorder associated with learning disability ranging from 2.8–4.5.

As result of the review of the studies, risks for co-morbidity associated with age, gender, severity of learning disability, and socioeconomic status remain uncertain.

Comorbidity of intellectual disability and mental disorder in children and adolescents: A systematic review, Einfeld S et al, in Journal of Intellectual and Developmental Disability, 36, 2 , 137-143