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Eur Arch Psychiatry Clin Neurosci. 2018 Mar;268(2):107-118. doi: 10.1007/s00406-017-0835-5. Epub 2017 Sep 11.

Chronobiological theories of mood disorder.

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Department of Psychiatry, Faculty of Medicine, Mansoura University, Mansoura, Egypt.
, 652 Dufferin Street, Toronto, ON, M6K 2B4, Canada.
University Sleep Disorders Center, College of Medicine, King Saud University, Riyadh, Saudi Arabia.
Somnogen Canada Inc, Toronto, ON, Canada.
BIOMED-UCA-CONICET and Department of Teaching and Research, Faculty of Medical Sciences, Pontificia Universidad Católica Argentina, Buenos Aires, Argentina.
Department of Psychiatry, Centre for Addiction and Mental Health, University of Toronto, Toronto, ON, M5T 1R8, Canada.


Major depressive disorder (MDD) remains the most prevalent mental disorder and a leading cause of disability, affecting approximately 100 million adults worldwide. The disorder is characterized by a constellation of symptoms affecting mood, anxiety, neurochemical balance, sleep patterns, and circadian and/or seasonal rhythm entrainment. However, the mechanisms underlying the association between chronobiological parameters and depression remain unknown. A PubMed search was conducted to review articles from 1979 to the present, using the following search terms: "chronobiology," "mood," "sleep," and "circadian rhythms." We aimed to synthesize the literature investigating chronobiological theories of mood disorders. Current treatments primarily include tricyclic antidepressants and selective serotonin reuptake inhibitors, which are known to increase extracellular concentrations of monoamine neurotransmitters. However, these antidepressants do not treat the sleep disturbances or circadian and/or seasonal rhythm dysfunctions associated with depressive disorders. Several theories associating sleep and circadian rhythm disturbances with depression have been proposed. Current evidence supports the existence of associations between these, but the direction of causality remains elusive. Given the existence of chronobiological disturbances in depression and evidence regarding their treatment in improving depression, a chronobiological approach, including timely use of light and melatonin agonists, could complement the treatment of MDD.


Chronobiology; Circadian rhythm; Light environment; Major depressive disorder; Melatonin; Mood disorder

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