Hypersomnia in inter-episode bipolar disorder: does it have prognostic significance?

BACKGROUND Hypersomnia in inter-episode bipolar disorder has been minimally researched. The current study sought to document the prevalence of hypersomnia in a sample of inter-episode patients with bipolar disorder and to examine the relationship between hypersomnia and future bipolar depressive symptoms. METHODS A total of 56 individuals with bipolar disorder (51 type I+5 type II) who were currently inter-episode, along with 55 non-psychiatric controls, completed a baseline assessment, including semi-structured interviews for psychiatric diagnoses, sleep disorders, and a battery of indices that included assessment of hypersomnia. Approximately 6 months later, participants were recontacted by telephone and mood was re-evaluated. RESULTS Three of six indices suggested that approximately 25% of participants with bipolar disorder endorsed symptoms of hypersomnia in the inter-episode period. Within the bipolar group, hypersomnia in the inter-episode period was associated with future depressive symptoms. This finding was independent of baseline depressive symptoms and medication use. LIMITATIONS Small sample size and concurrent psychopharmacology in the bipolar sample. DISCUSSION Though no gold standard measure for hypersomnia currently exists, this research takes a step towards identifying a clinically and empirically useful hypersomnia assessment. This study demonstrates that hypersomnia in the inter-episode period of bipolar disorder relates to future depressive symptoms, and adds to the growing body of evidence on the importance of inter-episode symptoms predicting bipolar relapse.