Abstract.: Objective: : It is not known whether the risk of recurrence declines with time in bipolar disorders and in major depression. This study describes the life-long recurrence risk of bipolar I, bipolar II and major depressive disorders. Method: : 160 bipolar-I, 60 bipolar-II and 186 depressive patients hospitalised between 1959 and 1963 were followed up every five years from 1965 to 1985. The course prior to the index hospitalisation was assessed in retrospect. The recurrence risk was computed by the multiplicative intensity model (Aalen et al. 1980). Results: : The cumulative intensity curves for the transition from states of remission to new episodes remained linear over 30 to 40 years after onset, indicating a constant risk of recurrence over the life-span up to the age of 70 or more. The recurrence risk of bipolar disorders (0.40 episodes per year) was about twice that of depression (0.20 episodes per year); BP-II disorders had only a slightly higher recurrence risk than BP-I disorders. There were no significant gender differences in the course of either bipolar or depressive disorders. Conclusion: : If long-term trials confirm its efficacy, these results support lifelong prophylactic treatment of severe types of mood disorder
