Objective: The authors of this study examined multiple recurrences of unipolar major depressive disorder.
Method: A total of 318 subjects with unipolar major depressive disorder were prospectively followed for 10 years within a multicenter naturalistic study. Survival analytic techniques were used to examine the probability of recurrence after recovery from the index episode.
Results: The mean number of episodes of major depression per year of follow-up was 0. 21, and nearly two-thirds of the subjects suffered at least one recurrence. The number of lifetime episodes of major depression was significantly associated with the probability of recurrence, such that the risk of recurrence increased by 16% with each successive recurrence. The risk of recurrence progressively decreased as the duration of recovery increased. Within subjects, there was very little consistency in the time to recurrence.
Conclusions: Major depressive disorder is a highly recurrent illness. The risk of the recurrence of major depressive disorder progressively increases with each successive episode and decreases as the duration of recovery increases.