Factor analysis of the Montgomery Asberg Depression Rating Scale in 251 bipolar II and 306 unipolar depressed outpatients.

Symptomatological differences between bipolar II (n = 251) and unipolar (n = 306) depressed outpatients, interviewed with the Structured Clinical Interview for DSM-IV, were studied by Montgomery Asberg Depression Rating Scale factor analysis. Different factors were found in bipolar II [factor 1 (apparent sadness, reported sadness), factor 2 (reduced sleep, reduced appetite), factor 3 (concentration difficulties, lassitude, inability to feel, pessimistic thoughts, and suicidal thoughts)], and in unipolar [factor 1 (apparent sadness, reported sadness, inability to feel, suicidal thoughts), factor 2 (concentration difficulties, lassitude, inability to feel, pessimistic thoughts), factor 3 (inner tension, reduced sleep)]. Different factor structure (between bipolar II and unipolar depression) supports previous findings that response to antidepressants and biology may be different in bipolar II and unipolar depression.