Objective: This study sought to describe, the natural history of major depressive disorder in a large group of nonclinical subjects. In particular, the analysis determined demographic and clinical risk factors for the recurrence of major depressive disorder.
Method: Relatives, comparison subjects (matched to relatives for age and sex), and spouses of affectively ill probands underwent structured clinical assessments before and after a 6-year interval.
Results: Of 396 individuals who had had only major depressive disorder that ended before the initial evaluation, 33.8% (N = 134) developed a new episode during the 6-year follow-up period. Youth, but not sex, was an important demographic risk factor. The presence of minor depression at the time of initial evaluation and the number of symptoms recalled from the worst previous episode were additional clinical risk factors. At the initial evaluation, 200 other subjects had described a previous history of both major depressive disorder and a nonaffective mental disorder. When compared to the subjects who recalled only a history of major depressive disorder, these subjects were more likely to have been in an episode of chronic intermittent depression at the initial evaluation and to recall a greater number of episodes as well as a greater number of symptoms in the worst episode. A history of a nonaffective mental disorder significantly increased the risk of relapse into major depressive disorder.
Conclusions: These findings agree well with a recent review of clinically based follow-up studies. Thus, youth and a history of nonaffective illness are important risk factors for the recurrence of major affective disorder in a broad variety of settings.