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It’s been known for a long time that winter-born babies are more likely to develop severe mental illness, including schizophrenia, depression and seasonal affective disorder.  Researchers at Vanderbilt and the University of Alabama may have identified clues as to how seasonal sunlight exposure could affect expression of clock genes that control our normal biological rhythms.

https://www.scientificamerican.com/article.cfm?id=blame-it-on-winter