Most community mental health services have evolved in response to the downsizing and closing of mental hospitals. Their form varies in different health care settings and their evolution was rarely subjected to formal evaluation. The introduction of Assertive Community Treatment in 1980 lead to a flurry of research activity which yielded conflicting results. Examination of these results provides the opportunity to distinguish essential from redundant components of care.

Two separate studies were conducted - a systematic review followed by cluster and regression analysis of reported components of care and a secondly a meta-regression analysis of published studies.

The meta-regression demonstrated that most of the variation in hospitalization outcome was due to differences in baseline hospital usage. Staffing levels (e.g. caseloads) were not found to be crucial but multi-disciplinary working and integrated psychiatrists were. The systematic review indicated the importance of integration of health and social care and outreach.

Multidisciplinary teams which include both social workers and psychiatrists and which focus on visiting patients at home are highly successful in managing severely ill patients in the community. Many of the detailed requirements proposed for ACT teams are probably superfluous.