Pattern of birth in restrictive and bulimic eating disorders.

Objective: To determine whether different eating disorders are associated with being born at different points in the year. Based on previous research, it was hypothesised that being born during warm months (June-August) is likely to be associated with restrictive anorexia, rather than bulimic disorders (bulimia nervosa, binge-purge anorexia).

Method: Case notes from 105 eating-disordered women were used to yield dates of birth and diagnosis. Associations were calculated between diagnostic group and birth period (month, quarter of year, high-risk quarter).

Results: Restrictive anorexics were significantly more likely than the bulimics (42.6% vs. 24.1%) to be born during the warmest quarter (June-August) than during the remainder of the year.

Conclusions: This preliminary study suggests that being born during warmer periods may form a small risk factor for the development of a restrictive eating disorder. Further research is suggested to test and extend the hypothesis.