Five-year course and outcome of dysthymic disorder: A prospective, naturalistic follow-up study.

OBJECTIVE: There have been few naturalistic follow-up studies of dysthymic disorder. This study describes the 5-year course and outcome of dysthymic disorder.
METHOD: The authors conducted a prospective, longitudinal follow-up study of 86 outpatients with early-onset dysthymic disorder and 39 outpatients with episodic major depressive disorder. Follow-ups, conducted 30 and 60 months after entry into the study, rated patients on the Longitudinal Interval Follow-Up Evaluation and the Modified Hamilton Rating Scale for Depression.
RESULTS: The estimated 5-year recovery rate from dysthymic disorder was 52.9%. Among patients who recovered, the estimated risk of relapse was 45.2% during a mean of 23 months of observation. Patients with dysthymic disorder spent approximately 70% of the follow-up period meeting the full criteria for a mood disorder. During the course of the follow-up the patients with dysthymic disorder exhibited significantly greater levels of symptoms and lower functioning and were significantly more likely to attempt suicide and to be hospitalized than were patients with episodic major depressive disorder. Finally, among patients with dysthymic disorder who had never experienced a major depressive episode before entry into the study, the estimated risk of having a first lifetime major depressive episode was 76.9%.
CONCLUSIONS: Dysthymic disorder is a chronic condition with a protracted course and a high risk of relapse. In addition, almost all patients with dysthymic disorder eventually develop superimposed major depressive episodes. Although patients with dysthymic disorder tend to show mild to moderate symptoms, from a longitudinal perspective, the condition is severe.