Mixed depression: a study of its phenomenology and relation to treatment response

Mixed depression reflects the occurrence of a major depressive episode with subsyndromal manic symptoms. Not recognized in DSM-IV, it is included in the proposed changes for DSM-5. Observational and cross-sectional studies have suggested that mixed depression is present in up to one-half of major depressive episodes, whether in MDD or bipolar disorder. Based on observational studies, antidepressants appear to be less effective, and neuroleptics more effective, in mixed than pure depression (major depressive episodes with no manic symptoms). In this report, we examine the specific manic symptoms that are most present in mixed depression, especially as they correlate with prospectively assessed treatment response.

In 72 patients treated in a randomized clinical trial (ziprasidone versus placebo), we assessed the phenomenology of manic symptom type at study entry and their influence as predictors of treatment response.

The most common symptom presentation was a clinical triad of flight of ideas (60%), distractibility (58%), and irritable mood (55%). Irritable mood was the major predictor of treatment response. DSM-based diagnostic distinctions between MDD and bipolar disorder (type II) did not predict treatment response.

In this prospective study, mixed depression seems to be most commonly associated with irritable mood, flight of ideas, and distractibility, with irritability being an important predictor of treatment outcome with neuroleptic agents. If these data are correct, in the presence of mixed depression, the DSM-based dichotomy between MDD and bipolar disorder does not appear to influence treatment response.