The Epidemiologic Catchment Area Program of the National Institute of Mental Health.

We hope that the ECA Program can make a significant, and perhaps unique, contribution to the field of psychiatric epidemiology and to mental health services research. If the Program provides total true prevalence data on mental disorders according to the latest diagnostic criteria, that in itself will be a significant contribution. Such data should be of enormous benefit to those interested in etiology as well as those interested in health services research. For researchers interested in etiology, the data can be used to identify, by comparison, high-risk groups; for those interested in health services research, the results can serve as a health planning guide that does not depend on the presence or absence of treatment facilities in a given area. Incidence data will be the second major contribution of the ECA Program. Its two-wave design enhances the study of incidence, etiology, and the natural history of disorders and also allows study of the social behavior of persons entering treatment for mental disorders--a subject important to health planners. Finally, a significant result of the ECA Program may be the establishment of a viable standardized methodology for the epidemiologic study of mental disorders by means of which demonstrably replicable results can be produced. Once we demonstrate the equivalence of method and results, then the stage is set for comparative studies of all sorts.