Cluster analytic validation of the DSM melancholic depression. The threshold model: integration of quantitative and qualitative distinctions between unipolar depressive subtypes

Cluster analysis was performed on the DSM-III symptoms of major depression and symptoms of melancholia identified in a study group consisting of 220 unipolar depressed inpatients a melancholic and non-melancholic cluster. Patients allocated to the melancholic cluster were more severely depressed and they were characterized by psychomotor disorders, a distinct quality of mood, diurnal variation, early morning awakening, and non-reactivity. Our results support the construct validity of the DSM-IlI melancholic subtype of major depression. This study supports the integrated threshold model: (i) melancholic and non-melancholic depression may be regarded as continuous classes in terms of overall severity of depression; and (ii) both groups form discrete categories with regard to the melancholic symptoms, which emerge as the severity of depression increases. (C) 1997 Elsevier Science Ireland Ltd.