Bipolar disorder in acute mood episodes showed circadian dysregulation due to phase shifts which returned to normal after treatment.
Acute manias were ~ 7 h circadian phase advanced, mixed manias were > 6 h delayed, whereas depressions were 4-5 h delayed compared to the controls.
Circadian dysregulation due circadian rhythm phase shifts might be a pathophysiological mechanism of bipolar disorder.
Bipolar disorder is a common mental disorder characterized by mood disturbances with alternating episodes of mania and depression. Circadian rhythms are rhythms of about 24 h found in many body functions. We repeatedly measured circadian rhythms in bipolar disorder patients during hospitalization. Acute manic episodes were associated with circadian dysregulation of ~ 7 hour phase advances, mixed manias were > 6 hour delayed, whereas bipolar depression was associated with 4–5 hour phase delays compared to the controls. After treatment, the shifted rhythms recovered to the normal range. This study suggests that novel chronotherapy approaches based on our findings might be found useful for the prevention and treatment of bipolar disorder.