Background. Depression is a remitting but recurring disease. However, there is a paucity of prospectively recorded data on the course of depression after recovery.

Method. A multi-centre prospective serial follow-up study of an inception cohort of hitherto untreated unipolar major depression (N=95) for 6 years. We report the time to recurrence after recovery from the index depressive episode and their predictors.

Results. The cumulative probability of remaining well without subthreshold symptoms was 57% (95% CI, 46 to 68%) at 1 year, 47% (95% CI, 36 to 58%) at 2 years and 35% (95% CI, 23 to 47%) at 5 years. The same without full relapse was 79% (95% CI, 70 to 88%) at 1 year, 70% (95% CI, 60 to 80%) at 2 years and 58% (95% CI, 46 to 70%) at 5 years. The median duration of well-interval from the end of the index episode to the beginning of the subthreshold episode was 19·0 months (95% CI, 2·4 to 35·7), and that to the end of the full episode was over 6 years. Residual symptoms at time of recovery predicted earlier recurrence.

Conclusions. The median length of the well-interval was much longer than previously reported in studies employing similar definitions but dealing with a more severe spectrum of patients. However, the sobering fact remains that less than half of the patients can expect to remain virtually symptom-free for 2 years or more after recovery from the depressive episode.