Objectives: To determine the prevalence of psychiatric disorders in adults with learning disabilities, and the relationship with severity of learning disabilities.

Method: The study is population-based. Detailed psychiatric assessments on 207 adults with learning disabilities living in Leicestershire, UK. were conducted by a learning disabilities psychiatrist, using the Present Psychiatric State - Learning Disabilities; and Disability Assessment Schedule. Diagnostic criteria are clearly defined. Developmental assessments were undertaken using the Vineland Scale (survey form).

Results: Psychiatric disorders were found in 49.2%, and rates for most individual disorders were higher than those found in the general population. Comparison with the two previous population-based studies shows the ascertained rates were broadly similar to those reported by Corbett but higher than those reported by Lund. Adults with more severe learning disabilities had higher rates of additional psychiatric disorders.

Conclusions: The results may be explained by a combination of the genetic, physical, psychological and social factors associated with learning disabilities also being aetiological to psychiatric disorders. The high prevalence rates of psychiatric disorders demonstrate the importance of health service provision for adults with learning disabilities.