Seasonal Pattern With Bipolar Disorder
In bipolar disorder (BD), the pathogenesis, clinical manifestations, and relapses are correlated with various abnormalities of circadian rhythm. Also in BD, there are incidences of recurrent infradian fluctuations of mood, social activity, weight, and sleep patterns. A seasonal pattern (SP) of disease course happens in about 25% and 15% of depressive and manic episodes. This is linked to more severe disease symptomatology. There is a need to understand the pathophysiological mechanisms of the seasonal impacts of BD. Researchers sought to review data on the underlying pathophysiological mechanisms of the seasonality of patients with BD, also suggesting future directions of research in this area of research.
Suprachiasmatic nuclei and the melatonergic and photoperiodism systems may play considerable roles in BD with SP. The interaction of clock gene vulnerabilities and biological clock neuroplasticity in addition to environmental factors may make BD with SP complex. A main role in BD with SP may be light, with the seasonal signaling pathways of light to the cortex serotonin transporter pathway and the pathway linking light to melatonin synthesis. Seasonality may also be closely linked to wider areas of BD. Researchers of this review suggest that future research should investigate markers of seasonality in BD including plasma melatonin, sleep–wake rhythms with actigraphy, and genetic or epigenetic variants in the melatonin synthesis pathway.
Reference: Maruani J, Anderson G, Etain B, Lejoyeux M, Bellivier F, Geoffroy PA. 2018. The neurobiology of adaptation to seasons: Relevance and correlations in bipolar disorders. Chronobiol Int. 35(10):1335-1353. doi:10.1080/07420528.2018.1487975