Adults with intellectual disabilities and mental illness in psychiatric inpatient units: empirical studies of patient characteristics and psychiatric diagnoses from 1996 to 2011

Background: Adults with intellectual disabilities still have limited access to psychiatric hospitalization when they experience mental illness. Knowledge about patients admitted to inpatient psychiatric units is still sparse. The objective of this review is to investigate patient characteristics and psychiatric diagnoses of adults with intellectual disabilities admitted to psychiatric inpatient units.Methods: A broad search of four electronic databases was conducted for relevant articles, which included controlled and naturalistic studies. The search was limited to articles published in English from 1996 through 2011.Results: Out of 310 hits, 72 articles were reviewed in full text and 19 were chosen for further analyses. Only empirical studies from psychiatric units admitting patients with intellectual disabilities and confirmed or suspected mental illness were considered. The included articles encompass about 4000 patients. Psychosis was the most common psychiatric diagnosis, followed by affective disorder and anxiety disorder. Behaviour problems were observed in a majority of the patients.Practical application: It appears that patients with intellectual disabilities and mental illness admitted to psychiatric inpatient units have especially complex conditions, which may include psychosis or affective disorder, challenging behaviour, often with additional physical conditions, and sparse verbal skills. More research is needed to develop suitable treatment for patients with intellectual disabilities in psychiatric inpatient settings.