Season of Birth as a Risk Factor

Abstract

A skeptic would be forgiven for thinking that the only that schizophrenia researchers agree on is that the disorder runs in families. Debate continues whether obstetric complications [1,2] and/or infections close to the time of birth [3] increase the for later After genetic factors, no single risk factor has been so consistently replicated as Tramer's original (1929) report [4] that being born in the winter/early spring months leads to an increased likelihood of developing schizophrenia some two decades later. Indeed, Jablenskey [5] described the season-of-birth effect as one of the most robust epidemiological findings in schizophrenia. Compared with genetic epidemiology, the season-of-birth effect does not imbue the research community with nearly as much enthusiasm. This may be because the seasonal effect size is small and has little predictive value, although Mortensen and colleagues [6] have pointed out the fallacy of such reasoning. An alternative reason for the apathy is that some researchers think the subject smacks of pseudoscience; yet Hippocrates encourages us; Whoever wishes to investigate medicine properly should proceed thus: In the first place to consider the seasons of the year and what effect each of them produces. It is now firmly established that a wide variety of human biological variables, from neurotransmitters and hormones to behaviors, may vary over 24hour periods, monthly and seasonally. Circadian rhythms, circaseptan rhythms, circatrigintan rhythms, and circannular rhythms are all part of the biological rhythms of the environment and the human life cycle. Reproductive behavior, ovulation and conception, follows a seasonal pattern. Ectopic