SHIFTS IN DIAGNOSTIC FREQUENCIES OF SCHIZOPHRENIA AND MAJOR AFFECTIVE-DISORDERS AT 6 NORTH-AMERICAN PSYCHIATRIC-HOSPITALS, 1972-1988

Objective: This study tested the impression that there have been signi ficant shifts in the relative diagnostic frequencies of schizophrenia and major affective disorders. Method: Data on discharge diagnoses fro m 1972 to 1988 were gathered from six North American psychiatric teach ing hospitals (data from one extended through 1991), and rates for sch izophrenia and major mood disorders were evaluated. Results: Total ann ual discharges increased by 6.6% during the study period. Large recipr ocal shifts in the frequencies of diagnoses of schizophrenia and major affective disorders were found, schizoaffective disorder was a minor diagnosis. Beginning in the early 1970s, a gradual increase in the fre quency of diagnoses of major affective disorders at all sites was acco mpanied by a corresponding decrease in diagnoses of schizophrenia at f ive of the six centers. Schizophrenia diagnoses decreased from a peak of 27% in 1976 to 9% in 1989 (a threefold decrease), and diagnoses of major affective disorders rose from a low of 10% in 1972 to 44% in 199 0 (a fourfold increase). Conclusions. Several forces may have influenc ed these changes. 1) DSM-III narrowed the definition of schizophrenia and broadened the category of major affective disorders. 2) Treatment- oriented diagnostic bias associated with the availability of lithium a nd other mood-altering agents may have encouraged consideration of aff ective disorders. 3) Economic and social forces, including better thir d-party reimbursement rates, may have favored affective diagnoses. 4) True increases in the incidence of affective disorders may have occurr ed. 5) Although a real decrease in new cases of schizophrenia may have occurred, this effect was probably minor and dominated by a larger sh ift of such diagnoses to affective categories.