Most processes of human body, such as brain function, are regulated by biological rhythms. Disturbance of biological rhythms impairs mood, behavior, cognition, sleep, and social activity and may lead to mental disorders. Disturbed rhythms are widely observable in patients with major depressive disorders (MDD) and make risk of onset, comorbidity, response of antidepressants, recurrence, cognition, social function, and complications of physical health. Therefore, it is crucial to assess and manage focus on biological rhythms for patients with MDD. There are several validated ways of assessing the biological rhythms, including 24 h fluctuations in cortisol or melatonin, sleep monitoring, actigraphy, and self-report scales. Chronotherapy, such as cognitive-behavioral therapy, interpersonal and social rhythm therapy, sleep deprivation, and bright light therapy was widely reported for treatment in patients with MDD. Monoamine antidepressants and lithium are attributed to regulation of biological rhythm. And some rhythm-regulated agents have been shown efficacy of antidepressant. Considering the crucial clinical significance of disturbed biological rhythms in MDD, we describe the mechanisms, clinical features, measurements, and treatments of the biological rhythms in patients with MDD.
Keywords: Biological rhythms; Chronotherapy; Circadian; Depressive disorder.