American tertiary clinic-referred bipolar II disorder versus bipolar I disorder associated with hastened depressive recurrence

Bipolar disorder (BD) is a chronic, frequently comorbid condition characterized by high rates of mood episode recurrence and suicidality. Little is known about prospective longitudinal characterization of BD type II (BD II) versus type I (BD I) in relation to time to depressive recurrence and recovery from major depressive episode. We therefore assessed times to depressive recurrence/recovery in tertiary clinic-referred BD II versus I patients. Outpatients referred to Stanford BD Clinic during 2000–2011 were assessed with Systematic Treatment Enhancement Program for BD (STEP-BD) Affective Disorders Evaluation and with Clinical Monitoring Form during up to 2 years of naturalistic treatment. Prevalence and clinical correlates of bipolar subtype in recovered (euthymic ≥8 weeks) and depressed patients were assessed. Kaplan–Meier analyses assessed the relationships between bipolar subtype and longitudinal depressive severity, and Cox proportional hazard analyses assessed the potential mediators. BD II versus BD I was less common among 105 recovered (39.0 vs. 61.0%, p = 0.03) and more common among 153 depressed (61.4 vs. 38.6%, p = 0.006) patients. Among recovered patients, BD II was associated with 6/25 (24.0%) baseline unfavorable illness characteristics/mood symptoms/psychotropics and hastened depressive recurrence (p = 0.015). Among depressed patients, BD II was associated with 8/25 (33.0%) baseline unfavorable illness characteristics/mood symptoms/psychotropics, but only non-significantly associated with delayed depressive recovery. BD II versus BD I was significantly associated with current depression and hastened depressive recurrence, but only non-significantly associated with delayed depressive recovery. Research on bipolar subtype relationships with depressive recurrence/recovery is warranted to enhance clinical management of BD patients.