A prospective, longitudinal study of percentage of time spent ill in patients with bipolar I or bipolar II disorders

Background: There is a recent appreciation that patients with bipolar disorder spend a substantial period of time with minor or subsyndromal mood symptoms both manic and depressive. This study examined time spent in minor and subsyndromal mood states as well as with mania and depression in a cohort of well characterized bipolar I and II patients who were followed prospectively for an average of three years. Method: Detailed life-charting data were obtained from 138 patients with bipolar disorder. Mood states were characterized as euthymic, subsyndromal, minor or major affective episodes based on rigorously defined criteria. The amount of time spent in these mood states during follow-up was examined. Results: Patients in the total sample and within each bipolar subtype spent approximately half of their time euthymic. The remainder of the time was spent in varying severity of mood states. However, the majority of time was spent with minor and subsyndromal symptoms, both manic and depressive. Bipolar I patients differ from bipolar II in that significantly more time was spent with subsyndromal, minor and manic symptoms. There was no difference in time spent with depressive symptoms between the two groups. Conclusions: Patients with bipolar disorder spend a substantial proportion of time with depressive or manic symptoms with the preponderance being minor or subsyndromal. Awareness of subthreshold symptoms in bipolar disorders and treatment of such symptoms may be improved by establishing guidelines that specifically outline appropriate strategies for reducing the duration of subsyndromal symptoms in bipolar disorder.