Factorial structure and factor reliability of the Hamilton Rating Scale for Depression.

Identical principal components factor analyses of total Hamilton Rating Scale for Depression scores were conducted for two separate sub-samples (N = 183 and N = 182) drawn from the same clinic population of moderately depressed outpatients. A comparison of the two factor analyses revealed substantial agreement for four factors across the two sub-samples (i.e., four factors from the first sub-sample correlated at least 0.80 with a homologous dimension in the second sub-sample). The four factors were labelled Somatic Complaints, Anorexia, Sleep Disturbance, and Agitation/Retardation. Some additional factors emerged in the analysis of one sub-sample but failed to appear in the other. Overall, these results suggest that the HRS exhibited a relatively stable factorial structure based on a large sample of outpatients with unipolar depressive disorders. Methodological problems with earlier research are discussed in light of the current findings.