Despite the fact they look like dying spiders, anorexic women see themselves as little whales. But, the disease goes beyond the morbid appearance: it determines hair loss, dry skin and osteoporosis; nails stop growing and a feeling of being overwhelmed settles in. Menstruation turns irregular and can even disappear for months; menopause comes early and spontaneous abortions can occur. Colitis and metabolic issues install, as well. About 10% of the anorexic women die because the failure of organs.

A new research revealed that even normal weight former-anorexic women have a different brain activity model than non-anorexic women. These individuals are worriers and perfectionists ever since childhood, and their brains are strongly driven by these deeply wired behavioral models.

Their anterior ventral striatum nucleus (connected to instant emotional responses) is less active in anorexic women, while the caudate nucleus (connecting actions to outcome and planning) is more active, thus anorexic women are more focused on the consequences of their choices, than on the reward. They cannot "live the moment", being concerned about making mistakes.

Now, a new research, published in "Archives of General Psychiatry", shows that males who have a twin sister seem to be more likely to develop anorexia nervosa than other males, even than males with a twin brother. It appears that exposure to female sex hormones in the uterus could indeed be connected to increased risk of anorexia nervosa.

"Anorexia nervosa is approximately 10 times more common in females than in males. 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." wrote the authors.

Dr. Marco Procopio, of the University of Sussex, Brighton, England, and Dr. Paul Marriott, of the University of Waterloo, Ontario, Canada, used information coming from a Swedish research, made on twins born between 1935 and 1958. Broader and more narrow diagnostic criteria revealed which twins experienced anorexia.

Female twins were more likely than male twins to be anorexic, excepting males who had a 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.

Out of the 4,478 opposite-sex twins, 20 females and 16 males had anorexia nervosa, as revealed by the narrow criteria, whereas 32 females and 27 males matched the broad criteria. The probability of these female twins to be anorexic was the same with 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. 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. The results of our study are compatible with the hypothesis that intrauterine exposure to sex hormones might influence neurodevelopment, affecting the risk of developing anorexia nervosa in adult life. This might be a factor contributing to the higher risk of developing anorexia nervosa in females." wrote the authors.