Babies born in spring are slightly more likely to develop anorexia nervosa, while those born in the autumn have a lower risk, say researchers.
A report published in the British Journal of Psychiatry, external suggests temperature, sunlight, infection or the mother's diet could be responsible.
Other academics said the effect was small and the disorder had many causes.
The researchers analysed data from four previous studies including 1,293 people with anorexia.
The researchers found an "excess of anorexia nervosa births" between March and June - for every seven anorexia cases expected, there were in fact eight.
There were also fewer than expected cases in September and October.
Dr Lahiru Handunnetthi, one of the report's authors, at the Wellcome Trust Centre for Human Genetics, said: "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 report suggests seasonal changes in temperature, sunlight exposure and vitamin D levels, maternal nutrition and infections as "strong candidate factors".
Dr Terence Dovey, from the Centre for Research into Eating Disorders, at Loughborough University, said: "Anorexia is a very complex multifaceted disorder," adding that the study looked at just one aspect.
"Should we concentrate screening methods to those born in the winter months? No, we should not. It leaves too much error of margin and the potential significant difference is only small."