The course and prognosis of manic-depressive psychosis: a quantitative analysis of episodes and intervals.

A quantitative analysis of episodes and symptom-free intervals in the course of manic-depressive psychosis was attempted. 1,066 patients who visited Tohoku University Hospital between 1955 and 1965 were investigated by a mail questionnaire and subsequent review of records in their care hospitals. There was no difference between the reply group and non-reply group in terms of demographic status. About 6.2% of patients were chronically ill. Eighteen percent of patients were dead at the time of study. The number of episodes was about three in depression and about seven in bipolar type during twelve years of observation. The length of symptom-free interval between episodes was about five years in depression and two years in bipolar type. There was no difference in the number of episodes or in the length of interval between 1955-1959 group and 1960-1965 group. The change of length was not confirmed between early and late intervals.