Abstract
Bipolar disorder (BD) is a severe and common neurodevelopmental psychiatric illness (1 to 4% of the general population). The severity and prognosis of this disease is partly linked to a high rate of recurrence of mood episodes with 70 to 80% relapses on average 2 years after a major episode (depressive or manic), despite treatments. These recurrences may follow a seasonal cyclicity for a significant number of patients. Almost all functions of the body are subject to the circadian rhythm, that is to say a 24-hour cycle. Thus, disorders of this rhythm can have consequences on sleep as well as on metabolism, the functioning of the cardiovascular system, the immune system as well as mood. However, the study of the effect of seasons in BD, presents a complex and heterogeneous literature, which to date does not benefit from an exhaustive synthesis. However, this article tends to improve knowledge of the influence of the biological clock on the symptoms of BD.
Keywords
Bipolar disorder, Circadian rhythms, Depression, Mania, Melatonin, Photoperiod, Pineal gland, Seasonal rhythms, Solar insolation, Suprachiasmatic nucleus