Clinical Features of Bipolar Depression Versus Major Depressive Disorder in Large Multicenter Trials

OBJECTIVE: Failure to recognize bipolar disorder in patients who experience a major depressive episode may lead to inappropriate treatment and poorer outcomes. Clinical features that could distinguish bipolar from unipolar depression would facilitate more appropriate treatment selection. METHOD: The authors used data from nonpsychotic outpatients participating in three large multicenter clinical trials conducted in the United States for the treatment of major depressive episodes to compare 477 subjects with a diagnosis of bipolar disorder and 1,074 with major depressive disorder. RESULTS: Bipolar depression was associated with family history of bipolar disorder, an earlier age at onset, a greater previous number of depressive episodes, and eight individual symptom items on the Montgomery-Åsberg Depression Rating Scale and the Hamilton Anxiety Rating Scale. Fears were more common in patients with bipolar disorder, whereas sadness; insomnia; intellectual (cognitive), somatic (muscular), respiratory, genitourinary complaints; and depressed behavior were more common in patients with unipolar depression. A logistic regression model correctly classified 86.9% of the subjects. CONCLUSIONS: Bipolar depression and major depressive disorder exhibit subtle differences in presentation, which may help guide the initial diagnosis.