Pattern of birth in adults with anorexia nervosa.

While women with anorexia nervosa are more likely to be born in March through June (in the northern hemisphere), there is no coherent model that explains this association. This study examined the birth pattern of adult restrictive and binge-purge anorexics and whether environmental temperature at assumed conception is a relevant factor. Retrospective analysis of the case notes of 195 adult anorexics was used to determine diagnosis, date of birth, eating attitudes, and body mass index. Meteorological records were used to determine temperature at assumed point of conception. Restrictive anorexics were significantly more likely than binge-purge anorexics to be born in April through June (, conceived July through September). A higher environmental temperature at the point of assumed conception was more likely to be found in restrictive anorexics than in anorexics of the binge-purge subtype. A higher environmental temperature at the assumed point of conception was associated with more restrictive eating attitudes during adulthood, but only among the restrictive anorexics. Possible explanations and implications of these findings are discussed.