An attempt to validate Akiskal's classification of chronic depression using cluster analysis.

A numerical taxonomy program that overcomes several problems often associated with cluster analysis was used in an attempt to validate Akiskal's classification of chronic depression. Whereas two of the four groups produced by this technique demonstrated features of either Akiskal's character spectrum disorder or chronic secondary depression, one group appeared to subsume both Akiskal's chronic primary depression and subaffective dysthymia. Within this group, early-onset patients exhibited characteristics of subaffective dysthymia and late-onset patients demonstrated features of chronic primary depression. Family history of depression and family history of alcohol dependence were potent discriminators between groups. There were points of similarity between the typology and several classifications of episodic depression, for example, Winokur's classification of unipolar depression and other typologies derived from multivariate analysis.