Patterns of treatment resistance in bipolar affective disorder.

The mean index episode length in 19 consecutive admissions with treatment-resistant bipolar affective disorder was 21.7 months. Four patterns of resistance were identified: rapid cycling (37%), other forms of cycling (32%), chronic depression (26%) and mixed states (6%). Female gender was significantly associated with rapid cycling. Other risk factors for treatment-resistant bipolar disorder, including a high prevalence of family history of affective disorder (72%) and electroencephalographic abnormalities (54% of recordings), were not confined to the rapid cycling group.