A longitudinal study of offset in the use of nonpsychiatric services following specialized mental health care.

This study examines the use of nonpsychiatric services by mentally ill persons following the receipt of specialized mental health care, frequently referred to as the "offset effect." A total of 9,761 persons enrolled during 1975 in the Columbia Medical Plan, a prepaid group practice in Columbia, Maryland, were studied over a 5-year period. Enrollees were classified into three groups: Treated--mental disorder diagnosis in 1975 and specialized mental health care in 1975; Untreated--mental disorder diagnosis in 1975 but no specialized mental health care in that year; and Comparison--neither mental disorder diagnosis nor specialized mental health care in 1975. The nonpsychiatric utilization for these groups was compared for 1973-1977. Specialized mental health care appears to have a short-term effect on nonpsychiatric utilization by attenuating the peak in use. Mentally ill persons without specialized mental health care in 1975 also reduced their use of nonpsychiatric services in 1976-1977. The utilization changes were more likely to occur in primary care departments, rather than nonpsychiatric specialty care departments. A diagnosis of mental disorder in either 1973 or 1974 was associated with a larger offset effect.