Sub-syndromal and syndromal symptoms in the longitudinal course of bipolar disorder

BACKGROUND: There have been few detailed longitudinal symptom studies of bipolar disorder. AIMS: To describe the course of bipolar disorder over 18 months in 204 patients receiving mental healthcare. METHOD: Patients were interviewed every 8 weeks, with weekly ratings of depression, mania and overall severity. RESULTS: Participants were symptomatic 53% of the time, with sub-syndromal symptoms present for twice as long as major disorder, and depressive symptoms three times more than manic symptoms. Individuals who were experiencing an episode at baseline spent 33% of the 18 months with substantial sub-syndromal symptoms, 17% with major disorder and 28% symptom free. Those not experiencing a baseline episode spent twice as long symptom free and half as long at disorder levels. Changes in symptom level were frequent. Predictors of sub-syndromal symptoms were similar to those of major disorder. CONCLUSIONS: Sub-syndromal residual symptoms are an important problem in recurrent bipolar disorder and require therapeutic intervention.