Season of birth
The time of a year in which a person is born has been linked to physiological and psychological changes to humans. Unlike Astrology, the scientific researches on the seasonality of births are usually trying to establish causal relationships (correlation ratios) with physical and mental health. Hippocrates recognized the importance of season of birth in 460 BC.
Scientific research in the field of seasonality of birth is one of the important and perspective concept in statistical human physiology and epidemiology. Despite the large number of works realized by research teams and individual researchers of different fields of physiology and medicine all this works trying to explain the reasons for discovered ratios of any hypothesis. It is the main cause of the impossibility of association results in a unified system of knowledge. It is worth considering the results of such research only how statistically accurate information; however, there is no consensus.
Birthdays submits to seasonality in itself (as example, a ranking based on how many babies were born in the United States on that date between 1973 and 1999).
The results of the scientific researches
Influence on medical conditions
The season in which babies are born can have a dramatic effect on their future risk relating to the development of conditions such as neurological disorders, including seasonal affective disorder, bipolar depression, schizophrenia and type I diabetes. Research has shown that the season a baby is born in can have a major effect on whether or not you will become a heavy smoker. This even varies between men to women.
As a factor in infant growth
The season during which a birth takes place has been linked to the weight development of the infant as well as initial weight.
As a factor in academic development
There is evidence that suggests that children who are born earlier while they attend the same academic year with others, gain an advantage:
- "In Britain the academic year begins in September, and there may be almost a year's chronological age difference between the eldest (September birthday) and youngest (August birthday) children in the same class. There is evidence that, in this context, children born in the autumn term (September to December birthdays) perform better academically, relative to their class peers, than those born in the spring term (January to April birthdays), who in turn outperform those born in the summer term (May to August birthdays)." 
As a suicide risk factor
Birth rates of people who later kill themselves show disproportionate excess for April, May and June compared with the other months. Overall, the risk of suicide increases by 17% for people born in the spring–early summer compared with those born in the autumn–early winter; this risk increase was larger for women (29.6%) than for men (13.7%).
Research works in Sweden show that those who preferred hanging rather than poisoning or petrol gases were significantly more likely to be born during February–April. Maximum of the month-of-birth curve for preferring hanging was for March–April and the minimum was for September–October.
- The Daily Viz. 05/12/2012. Matt Stiles. How Common Is Your Birthday?
- Season of birth defines personality
- Y. Zheng, H. Pan, D. Ye. Season of birth: A potential influential factor for quality of life.Medical Hypotheses, Volume 72, Issue 5, Pages 609-610. 
- The New York Times. December 19, 2006. How Common Is Your Birthday? Source: Amitabh Chandra, Harvard University 
- PE Watson and BW McDonald (2007). Seasonal variation of nutrient intake in pregnancy: effects on infant measures and possible influence on diseases related to season of birth European Journal of Clinical Nutrition 61, 1271–1280; doi:10.1038/sj.ejcn.1602644 [saurav kumar http://www.nature.com/ejcn/journal/v61/n11/abs/1602644a.html]
- Riala, Kaisa; Helinä Hakko; Anja Taanila; Pirkko Räsänen (2009). "SEASON OF BIRTH AND SMOKING: FINDINGS FROM THE NORTHERN FINLAND 1966 BIRTH COHORT". Chronobiology International. 26 (8): 1660–1672. doi:10.3109/07420520903534484. Retrieved 14 October 2011.
- "Season Of Birth May Be Factor In Infant Growth"
- Russell and Startup, (1986), found in: Ford, J. G. T. & Goodman, R. (2002) Does season of birth matter? The relationship between age within the school year (season of birth) and educational difficulties among a representative general population sample of children and adolescents (aged 5-15) in Great Britain. Research in Education 
- E. Salib and M. Cortnia-Borja. Effect of month of birth on the risk of suicide. The British Journal of Psychiatry, May 1, 2006; 188(5): 416 - 422. 
- Chotai J, Salander Renberg E. Season of birth variations in suicide methods in relation to any history of psychiatric contacts support an independent suicidality trait. J Affect Disord 2002; 69: 69-81. (CrossRef)