Early- versus late-onset dysthymic disorder: Comparison in out-patients with superimposed major depressive episodes

Background: This study examined the validity of the early-late onset subtyping distinction in dysthymic disorder. Methods: Participants were 340 out-patients meeting DSM-III-R criteria for dysthymia and a concurrent major depressive episode (MDE). The sample was drawn from a 12-site double-blind randomized parallel group trial comparing the efficacy of sertraline and imipramine in the treatment of chronic depression. All patients received comprehensive evaluations using semi-structured interviews and rating scales. Results: 73% of the sample met criteria for the early-onset, and 27% for the late-onset, subtype. The early-onset patients had a significantly longer index MDE, significantly higher rates of personality disorders and lifetime substance use disorders, and a significantly greater proportion had a family history of mood disorder. The subgroups did not differ in symptom severity or functional impairment at baseline, nor in response to a 12-week trial of antidepressants. Limitations: Further work is needed to extend these findings to dysthymic disorder without superimposed MDEs. Conclusions: These results support the distinction between early-onset and late-onset dysthymic disorder.