Self rated depression in relation to DSM-III classification: a statistical isolinear multiple components analysis

The Zung Self-Rating Depression Scale (SDS) was presented to 99 depressed inpatients. The patients were categorized according to DSM-III as suffering from minor depression, major depression without melancholia and major depression with melancholia and/or with psychotic features. Differences in self-reported symptoms between these categories were studied with multivariate statistical techniques including linear discriminant analysis (LDA) and statistical isolinear multiple components analysis (SIMCA). Patients with minor depression rate themselves significantly less depressed than those with major depression. Patients with major depression without melancholia are less depressed than those with melancholia and/or psychotic features. The three DSM-III depressive categories can be regarded as belonging to a clinical continuum in which they form relevant levels with quantitative differences in self-reported symptoms. These differences are not only defined by gradual shiftings in the overall severity of illness, but also by quantitative differences in the severity of some target symptoms, i.e. agitation, retardation, diurnal variation, loss of libido, fatiguability, insomnia, anorexia, sadness and anhedonia.