If you were born in the spring, your chances of subsequently developing anorexia are greater, researchers from the Wellcome Trust Centre for Human Genetics, University of Oxford, revealed in the British Journal of Psychiatry. According to the authors, theirs is the "largest study to date" and provides compelling evidence of a link between spring births and anorexia risk.
Dr Lahiru Handunnetthi and team gathered data including birth dates of 1,293 individuals who had been diagnosed with anorexia. They discovered that a disproportionately high number of patients (15% excess) were born between March and June, for every seven anorexia cases expected, there were eight. They also found fewer-than-expected births in September/October (20% deficit).
The researchers explain that previous studies had indicated a risk between developing an eating disorder and when the person is born. However, they were small studies involving few people - making it difficult to come to any conclusions.
Dr Handunnetthi said:
"We meta-analysed four cohorts of anorexia nervosa patients from the UK, making this the largest ever study to assess the presence of a season of birth effect in anorexia. We found that susceptibility to anorexia nervosa is significantly influenced by a person's season of birth, being higher in those people born in the spring and lower in those born in the autumn.
A number of previous studies have found that mental illnesses, such as schizophrenia, bipolar disorder and major depression are more common among those born in the spring - so this finding in anorexia is perhaps not surprising. However, our study only provides evidence of an association. Now we need more research to identify which factors are putting people at particular risk."
The scientists say that perhaps environmental factors which are present when conception occurs, or during fetal development in the uterus, may have an impact.
Dr Handunnetthi said:
"Seasonal changes in temperature, sunlight exposure and vitamin D levels, maternal nutrition and exposure to infections are all possible risk factors. Identifying these risk factors is important in helping us understand and maybe even prevent illness in future."
"Season of birth and anorexia nervosa"
Giulio Disanto, MD, Adam E. Handel, BMBCh and Andrea E. Para, MSc
Written by Christian Nordqvist