How your birthday may be related to bulimia and binging

Could the season in which you were born be related to your eating disorder? A study published this month suggests that bulimia and binge eating are correlated with a fall birthday.

The study was conducted by Dr. Timothy Brewerton and colleagues. They interviewed over 3,000 women from across the United States asking about eating disorder symptoms. Based on the interviews, they were able to identify women who met criteria for bulimia nervosa at some point in their life. Statistical tests were conducted to see if there were significant differences in the season of birth between women with a lifetime history of bulimia and women who never met criteria for bulimia. Indeed, women with bulimia were born in the fall (Sep 22 – Dec 21) significantly more often than women without a lifetime history of bulimia. This means that chance alone couldn’t account for the relationship between bulimia and a fall birthday.

The researchers also found similar results for women who reported binge eating at some point in their lives. These women were born in the fall significantly more often than women who never binged.

Does this mean giving birth to a daughter in the fall increases her chances of developing bulimia? No – because the study simply looked at the correlation between a fall birthday and bulimia and does not show that a fall birthday causes bulimia.

Dr. Brewerton and his colleagues can’t explain exactly why there’s a correlation between fall birthdays and bulimia, but they offer a few ideas. It might have something to do with time of conception, the amount of sunshine during the baby’s development, or seasonal variations in infections during pregnancy or birth. They also suggest it could have something to do with the fact that girls born in the fall tend to be older than other students in their grade (e.g. a girl with an October birthday is older than her classmate with a June birthday based on the typical U.S. academic calendar). However, these ideas are simply speculations and there isn’t any scientific evidence to explain the relationship between a fall birthday and bulimia.

UPDATE 2013: Researchers tried to replicate the results of the above study without success. Two independent studies published in 2013 did not find any relationship between suffering from bulimia and being born in the fall; the first was published in the European Eating Disorders Review and the second in the International Journal of Eating Disorders.

Photo credit: Will Clayton

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Dr. Gupta is a professor at Barnard College of Columbia University and provides individual therapy at Tribeca Psychology

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