The persistent risk of chronicity in recurrent episodes of nonbipolar major depressive disorder: a prospective follow-up.

The authors report on the course of illness in 101 patients who were in an episode (the "index episode") of major depressive disorder when they entered a clinical research study, recovered from that episode, and then relapsed into a new episode (the "first prospective episode") of the disorder. They found a 22% probability that these patients' first prospective episode would last at least 1 year, similar to the 21% rate of chronicity previously reported for the index episode. A long prior episode, older age, and low family income were found to predict chronicity in the first prospective episode.