WHY ARE DEPRESSION AND ANXIETY CORRELATED - A TEST OF THE TRIPARTITE MODEL

L. A. Clark and D. Watson's (1991) tripartite model groups the symptom s of depression and anxiety into 3 components: nonspecific symptoms of general distress, which do not distinguish depression and anxiety; ph ysiologic arousal, which is relatively unique to anxiety; and anhedoni a(or low positive affect), which is unique to depression. Structural e quation modeling was used to test this model with self-report data fro m 3 different samples: outpatients seeking treatment for mood disorder , anxiety disorder, or both (n = 483), out patients seeking treatment for substance abuse (n = 453), and college students (n = 516). The tri partite model did not fit any of the sample covariance matrices, becau se the nonspecific symptoms of depression and anxiety could not be ade quately represented by a single General Distress factor. An alternativ e model, in which the Anhedonia and Nonspecific Depression factors loa ded on a second-order Depression factor, while the Somatic Arousal and Nonspecific Anxiety factors loaded on a second order Anxiety factor, produced an excellent fit in all the groups. The Nonspecific Depressio n and Nonspecific Anxiety factors were the most valid and specific ind icators of depression and anxiety, respectively. Anhedonia and Somatic Arousal were significantly less valid measures of depression and anxi ety. The implications of these findings are discussed.