Long-term course of bipolar I and II disorders: chronicity, dimensionality and relapse

Studies of the longitudinal natural history of the long-term course of illness (up to 20 years) of patients with bipolar I (BP-I) and bipolar II (BP-II) have found that both disorders are highly chronic. BP-l patients were symptomatic from their illness only 47% of the weeks and BP-II patients were symptomatic 54% of the weeks. All levels of depressive and manic symptom severity ranging from the subsyndromal to syndromal level fluctuated frequently within the same bipolar patient over time, indicating that both BP-I and BP-II disorders are symptomatically expressed across time as dimensional illnesses. Minor and subsyndromal manic and depressive symptoms were 3 times more common than syndromal level symptoms of mania and major depression. Depressive symptoms were three times more common than manic during the course of BP-I patients, and BP-II is overwhelmingly a depressive illness in which depressive symptoms are over 30 times more common than symptoms in the manic spectrum. Examination of hypomanic episodes in BP-II revealed that hypomanias of short duration (2-6 days) compared to long duration (more than 6 days) are not clinically significantly different and appear to be part of the same disease process. Detailed analyses of psychosocial impairment during the course of bipolar illness show that affective symptom severity and psychosocial disability increase and decrease in parallel. Depressive symptoms are equally disabling in BP-I and BP-II, often more disabling than manic/hypomanic symptoms. When asymptomatic, BP-I and BP-II patients' psychosocial function normalizes and no disability is present. Recovery from episodes in BP-I and BP-II with ongoing residual subsyndromal affective symptoms is associated with risk for very rapid relapse. Thus, all levels of affective symptom severity, including subsyndromal, are legitimate targets for therapeutic intervention to reduce risk of relapse and disability. The predominance of depressive symptoms indicates that more emphasis should be placed on the identification and management of depressive symptoms that present in patients with bipolar I and II disorders.