Males with a female twin may be at higher risk for anorexia nervosa

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, one of the JAMA/Archives journals. 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.

Overall, female twins were more likely than male twins to develop anorexia nervosa. The one exception was among males who had a dizygotic (fraternal) twin sister. “In fact, their risk is at a level that is not statistically significantly different from that of females from such a pair,” the authors write. Among 4,478 dizygotic opposite-sex twins, 20 females and 16 males had anorexia nervosa using narrow criteria and 32 females and 27 males qualified under the broad criteria. Risk for these female twins was not significantly different from than that of other female twins.

“A plausible explanation for this phenomenon is that in pregnancies bearing a female fetus, a substance is produced, probably hormonal, that increases the risk of having anorexia nervosa in adulthood,” the authors write. “Because the male half of an opposite-sex twin pair would also be exposed to this substance, it could account for the observed elevated risk in males with female twins. The most likely candidates are sex steroid hormones.”

Source: JAMA and Archives Journals

Related stories:

Research indicates testosterone could guard against eating disorders
Testosterone appears to protect people against eating disorders, providing further evidence that biological factors -- and not just social influences -- are linked to anorexia and bulimia, according to new research findings at Michigan State University.
Study finds gender differences related to eating and body image
Researchers have discovered a subtle new difference between men and women – this one occurring in the realm of eating.
New CT technology shows anorexia impairs adolescent bone development
Children and teenagers with even mild cases of anorexia exhibit abnormal bone structure, according to a new study appearing in the December issue of Radiology and presented at the annual meeting of the Radiological Society of North America (RSNA).
Pregnant women with bulimia have more anxiety and depression
Women who have bulimia in pregnancy have more symptoms of anxiety and depression compared to pregnant women without eating disorders. A new study from the Norwegian Institute of Public Health (NIPH) shows that they also have lower self-esteem and are more dissatisfied with life and their relationship with their partner.
Psychiatry research: When the mirror becomes an enemy
A nose that's too big, hair that's too curly or a beauty mark in the wrong place – who hasn't focused on a small detail of their appearance while staring at a mirror?
Survey: 'Tanorexia' common among university students
A new study conducted at a large university finds more than 25 percent of those surveyed reported symptoms of tanning dependence, including symptoms similar to alcohol and drug-addicted individuals. Suggestively, the study also found those with a tanning dependence tend to be more likely to be thin and smoke cigarettes than others. The study by researchers at Fox Chase Cancer Center is published in the September/October issue of the American Journal of Health Behavior.
Sleight of hand and sense of self
(PhysOrg.com) -- An illusion that tricks people into believing a rubber hand belongs to them isn’t all in the mind, Oxford University researchers have found. They have observed a physical response as well, a finding that offers insight into conditions which affect a patient’s sense of self and body ownership, such as stroke, schizophrenia, autism, or eating disorders.
Looking for the Founatain of Youth? Cut your calories, research suggests
Want to slow the signs of aging and live longer? New Saint Louis University research suggests cutting back on calories could be a promising strategy.

News discussion:

Medicine & Health news