General psychiatric services for adults with intellectual disability and mental illness

Background Adults with intellectual disability (ID) and mental illness may use general or specialist psychiatric services. This review aims to assess if there is evidence for a difference in outcome between them. Methods A literature review was conducted using a variety of electronic databases and hand‐search strategies to identify all studies evaluating the outcome of people with ID and mental illness using general psychiatric services. Results There is no conclusive evidence to favour the use of general or specialist psychiatric services. People with ID stay less time on general psychiatric than specialist inpatient units. People with severe ID appear not to be well served in general services. Older studies of inpatient samples suggest a worse outcome for people with ID. Novel specialist services generally improve upon pre‐existing general services. Assertive outreach in general services may preferentially benefit those with ID. Recent studies suggest similar lengths of stay in general psychiatric beds for people with and without ID. Conclusions Although 27 studies were located, only two were randomized controlled trials. The evidence is poor quality therefore further evaluation of services employing a variety of designs need to be employed to give more robust evidence as to which services are preferred.