Sleep, illness course, and concurrent symptoms in inter-episode bipolar disorder.

We investigated associations between sleep, illness course, and concurrent symptoms in 21 participants with bipolar disorder who were inter-episode. Sleep was assessed using a week-long diary. Illness course and symptoms were assessed via validated semi-structured interviews. Lower and more variable sleep efficiency and more variable total wake time were associated with more lifetime depressive episodes. Variability in falling asleep time was positively correlated with concurrent depressive symptoms. Sleep efficiency was positively correlated with concurrent manic symptoms. These findings suggest that inter-episode sleep disturbance is associated with illness course and that sleep may be an important intervention target in bipolar disorder.