TREATED PREVALENCE RATES OF SEVERE MENTAL-ILLNESS AMONG HMO MEMBERS

Objectives, The authors examined the extent to which health maintenanc e organizations (HMOs) enroll and provide services to PeoPle with seve re mental illness. Methods: The automated pharmacy system of a large H MO identified members who had received a Prescription for an antipsych otic drug or lithium during the two-year study period (1986 and 1987). These data, combined with data from a 2 percent random sample of HMO members and from medical records, were used to identify members who sa tisfied DSM-III-R criteria for schizophrenia and bipolar disorder. Tre ated prevalence rates derived from these data were compared with estim ated treated prevalence data obtained in the National Institute of Men tal Health's Epidemiologic Catchment Area (ECA) survey. Results: Altho ugh methodological complications and small sample sizes precluded a de tailed comparison, the study found a significantly lower treated preva lence rate of schizophrenia among HMO members than in the ECA survey. The treated prevalence rate of bipolar disorder was also lower than th e ECA rate, but the difference was not significant. Conclusions: The d ifferences in treated prevalence rates seemed to be the result of diff erent study methodologies and factors influencing HMO membership. The results underscore the need for a comprehensive study of the course of severe mental illness among HMO members.