Risk for bipolar illness in patients initially hospitalized for unipolar depression

Objective: To assess the risk for subsequent development of mania or hypoma nia, the authors conducted a 15-year prospective follow-up study of a large , young cohort of patients originally hospitalized for unipolar major depre ssion. Method: Patients who were hospitalized for unipolar major depression (N=74 mean age=23.0 years, SD=3.8) were assessed prospectively as inpatients and then followed up five times over IS years, at approximately 2, 5, 8, 11, an d 15 years after discharge. Manic or hypomanic episodes, medications, and r ehospitalizations were determined by standardized assessments at each follo w-up. Polarity conversions were evaluated by survival analyses. Results: By the 15-year follow-up, 27% of the study group had developed one or more distinct periods of hypomania, while another 19% had at least one episode of full bipolar I mania. Depressed patients with psychosis at the i ndex depressive episode were significantly more likely than nonpsychotic pa tients to demonstrate subsequent mania or hypomania at follow-up. Those wit h family histories of bipolar illness showed a nonsignificantly higher rate of switching to mania or hypomania. Spontaneous and antidepressant-associa ted manias did not differ in frequency. Fewer than one-half of the patients who showed an eventual bipolar course had received prescriptions for mood stabilizers in any follow-up year. Conclusions: Young depressed inpatients with psychotic features may be at e specially high risk for eventually developing mania. The probability for de veloping a bipolar spectrum disorder increases in linear fashion for patien ts at risk for polarity conversion during the first 10-15 years after an in dex depressive episode.