Bipolar spectrum disorder: a pilot study

To assess depressive features of a proposed definition of bipolar spectrum disorder (BSD).

Thirty-six patients with bipolar disorder type I or II were compared to 37 patients with unipolar major depressive disorder through patient interview and chart review.

Univariate analysis suggests that 7 of 12 (recurrent major depressive episodes, brief major depressive episodes, atypical depressive symptoms, early age of onset, family history of bipolar disorder, antidepressant tolerance, and antidepressant-induced mania) features of major depressive episodes were more likely to occur in bipolar versus unipolar patients. After adjustment in a multivariable regression model, however, the five most powerful predictors of bipolar disorder were brief major depressive episodes, early age of onset, antidepressant- induced mania, postpartum depression, and atypical depressive symptoms.

This preliminary study supports the idea that bipolar disorder is characterized by some depressive features less likely to be found in unipolar depression. Further prospective study needs to be conducted comparing BSD with unipolar depression.