Objective: To compare the personality traits and disorders of patients with bipolar II disorder and major depression and to examine the impact on treatment outcome of a bipolar II diagnosis.
Method: Patients from two clinical trials, a depressive sample (n = 195, 10% bipolar II) and a bulimic sample (n = 135, 16% bipolar II), were assessed for personality traits using DSM-IV criteria. Patients were randomised to treatments (fluoxetine or nortriptyline for depressive sample; cognitive behaviour therapy for bulimic sample) and followed for 3 years (depressive sample) or 5 years (bulimic sample) to assess the impact on outcome of a bipolar II diagnosis.
Results: Bipolar II patients were assessed as having more borderline, histrionic and schizotypal personality traits than patients with major depression. A baseline bipolar II diagnosis did not impact negatively on treatment outcome, and less than 5% of bipolar II patients developed bipolar I disorder during follow up.
Conclusions: The low rate of conversion of bipolar II to bipolar I disorder and the lack of adverse impact of the diagnosis on outcome, questions the need for antimanic or mood stabiliser medication in most bipolar II patients.