To compare the course of depression during a 2-year period in adult outpatients (n=626) with current major depression, dysthymia, and either both current disorders ("double depression") or depressive symptoms with no current depressive disorder.
Depressed patients visiting 523 clinicians (mental health specialists and general medical providers) were identified using a two-stage screening procedure including the Diagnostic Interview Schedule. The course of depression was assessed in 2 follow-up years with a structured telephone interview based on the format of the Diagnostic Interview Schedule.
Baseline severity of depressive symptoms was greatest in patients with double depression, but initial functional status was poor in those with dysthymia with or without concurrent major depression. Patients with dysthymia had the worst outcomes, those with current major depression alone had intermediate outcomes, and those with subthreshold depressive symptoms had the best outcomes. Even the latter group, however, had a high incidence (25%) of major depressive episode over 2 years. Initial depression severity and level of functional status accounted for more explained variance in outcomes than did type of depressive disorder.
The findings emphasize the poor prognosis associated with dysthymia even in the absence of major depression; the prognostic significance of subthreshold depressive symptoms; and the clinical significance of assessing level of severity of symptoms as well as functional status and well-being,` regardless of type of depressive disorder.