The epidemiology of treatment for chronic and nonchronic mental disorders.

To estimate the annual treated incidence and prevalence of chronic and nonchronic mental disorders, data from the Monroe County Psychiatric Register were analyzed. Patients were classified as either chronic or nonchronic based upon their utilization of inpatient psychiatric treatment. A chronic illness was defined as one requiring at least three psychiatric hospitalizations or at least 365 inpatient days during a 5-year follow-up period. Based upon this definition, the annual treated incidence of chronic mental disorders did not change significantly between 1964-65 (.47/1000) and 1969-70 (.41/1000), unlike the annual treated incidence of nonchronic disorders, which rose by 37 per cent (p less than .001). The annual treated prevalence of chronic mental disorders also remained unchanged at approximately .6 per cent between 1965 and 1970, but the treated prevalence of nonchronic mental disorders rose by 43 per cent from 1.4 per cent in 1965 to 1.9 per cent in 1970 (p less than .01). These increases in treatment for nonchronic disorders coincided with the development of community mental health centers. The rates of chronicity and peak ages of treatment varied considerably across diagnostic groups. Approximately one fifth of new cases of organic brain disorders, schizophrenia, and alcohol disorders became chronic according to our definition during the first 5 years after illness onset, compared to only 9 to 11 per cent of cases of major affective disorders and less than 2 per cent of all other disorders.(ABSTRACT TRUNCATED AT 250 WORDS)