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

Abstract

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.