"Double depression": two-year follow-up.

Of 316 patients with a major depressive disorder who were followed for between 6 months and 2 years, 80 (25%) had a preexisting chronic minor depression of at least 2 years' duration. The chronic minor depression reduced the apparent effect of the known predictors of recovery and relapse from the major depressive disorder and predicted a very pernicious course for the chronic depression. Furthermore, the longer the patient continued to suffer from a chronic minor depression after recovering from the major depression, the greater the probability that relapse into another major depression would preempt recovery from the chronic depression.