Circadian rhythms and sleep in bipolar disorder: implications for pathophysiology and treatment

Purpose of review Multiple lines of evidence support the conceptualization of bipolar disorder as a disorder of circadian rhythms. Considering bipolar disorder in the framework of circadian disturbances also helps understand the clinical phenomenology pointing toward a multisystemic involvement. Recent findings Patients with bipolar disorder show altered rhythmicity in body temperature and melatonin rhythms, high day-to-day variability in activity and sleep timing, persistent disturbances of sleep or wake cycles, including disturbances of sleep continuity. The internal clocks are, indeed, responsible for regulating a variety of physiologic functions, including appetitive behaviors, cognitive functions and metabolism. Summary An underlying circadian pathology in bipolar disorder is a unifying explicatory model for the high psychiatric and medical comorbidity observed during the long-term course of the disorder. This model also provides a rationale for therapeutic interventions aimed at re-entraining the internal clock.