Associations between season of birth and suicide: a brief review.

Suicide is a complex behaviour contributing to a significant number of unnecessary deaths worldwide. Accordingly, the quest for suicide risk factors is one of the most intensively developing issues of psychiatric research. In the last few decades a number of interesting results have been published about associations between season of birth (SOB) and several physiological and pathological aspects of human life, while, in regard to neuroscience, several investigations confirmed that SOB is associated with the risk of several major neuropsychiatric disorders and suicide as well. Research concerning the possible causative factors behind these associations were also performed suggesting that SOB-associated factors (including day length; seasonal changes in maternal nutritional status and vitamin D levels; seasonal alterations in incidence of some common infective disorders) contribute to neurochemical and consequentially temperament/personality trait alterations which may mediate the associations between SOB and psychiatric disorders. Other results indicate an uneven distribution of monoamine metabolism-related genotypes in different birth season cohorts possibly underpinning the effects of SOB. In our narrative review we summarize and discuss the available literature on the relevance of the most important findings concerning the above fields.