The nosology of chronic depression has become increasingly complex since the publication of the revised third edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-III-R; American Psychiatric Association, 1987), but there are few data available to evaluate the validity of the distinctions between the subtypes of chronic depression. The validity of the distinction between DSM-III-R chronic major depression (CMD) and major depression superimposed on dysthymia (double depression, DD) was examined. Participants were 635 patients with chronic depression in a 12-week trial of antidepressant medications. Patients with CMD, DD, and a 3rd group with a chronic major depressive episode superimposed on dysthymia (DD/CMD) were compared on demographic and clinical characteristics, family history, and response to treatment. Few differences were evident, although the depression of patients with DD/CMD tended to be more severe.
