Males who have a twin sister appear more likely to develop the eating disorder anorexia nervosa than other males, including those with a twin brother, according to a report in the December issue of Archives of General Psychiatry.
This finding supports the hypothesis that exposure to female sex hormones in the womb may be related to the risk for anorexia nervosa.
“Anorexia nervosa is approximately 10 times more common in females than in males,” the authors write as background information in the article. “The reasons for this difference are not known, and it is likely that their unraveling will represent an important step forward in the understanding of the etiopathogenetic factors involved in the development of eating disorders.”
Marco Procopio, M.D., M.R.C.Psych., of the University of Sussex, Brighton, England, and Paul Marriott, Ph.D., of the University of Waterloo, Ontario, Canada, analyzed data from a study of Swedish twins born between 1935 and 1958. Two sets of diagnostic criteria, one broader and one more narrow, were used to determine which twins had anorexia nervosa.