The relationship between anxiety and depression. A review of some principal component analytic studies.

Forty studies published between 1934 and 1977 which used principal component analysis of symptoms, personality or illness features in patients with affective disorders were examined. Factor clusters or dimensions indicative of anxiety and depression were evident in each study. Visual plots on the first 2 components in each of 6 studies selected as being representative of the 40 are included in this paper. The implications arising from semantic confusion are discussed.