Bipolar II disorder: personality and outcome in two clinical samples

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.

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.

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.

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.