• adolescents;
  • adults;
  • bipolar disorder;
  • children;
  • hypersomnia;
  • insomnia;
  • sleep

The aim of this article is to highlight the importance of the sleep–wake cycle in children, adolescents, and adults with bipolar disorder. After reviewing the evidence that has accrued to date on the nature and severity of the sleep disturbance experienced, we document the importance of sleep for quality of life, risk for relapse, affective functioning, cognitive functioning, health (sleep disturbance is implicated in obesity, poor diet, and inadequate exercise), impulsivity, and risk taking. We argue that sleep may be critically important in the complex multifactorial cause of interepisode dysfunction, adverse health outcomes, and relapse. An agenda for future research is presented that includes improving the quality of sleep measures and controlling for the impact of bipolar medications.