Prenatal exposure to female hormones increases the risk of anorexia nervosa, according to new research released Monday that bolsters the theory that the disorder has a biological basis in addition to a social and cultural one.
In an analysis of 4,478 pairs of opposite-sex twins, researchers found that the males had the same chance of becoming anorexic as women in general, an indication that hormones circulating in their mother's womb increased their susceptibility to the disorder.
The study, published in the Archives of General Psychiatry, shed new light on the causes of the eating disorder, which is often linked to a cultural obsession with thinness and is 10 times as common in women than men.
"Any information that points to a biological origin is helpful, at least for future development of medication and other therapies," said Dr. Thomas Weigel, a psychiatrist who treats eating disorders at McLean Hospital in Belmont, Mass.
"If there is medical origin, that suggests a medical solution," said Weigel, who was not connected to the study.
An often intractable disorder, anorexia affects about 1% of females in the United States and leads to death in 10% of the cases. People with anorexia are obsessed with body weight and diet to the point of starving themselves. About half the people with the disorder binge on food and then purge it (inducing vomiting, taking laxatives and diuretics, or both). The other half restricts food intake and exercises excessively.
Standard treatment for the disorder is behavioral therapy, and in severe cases, patients are hospitalized to restore their weight. The relapse rate in the worst cases is high, and half are readmitted within a year.
The disorder has long been seen as a consequence of a culture that equates beauty with thinness. People involved in activities that emphasize weight or body image, such as modeling, ballet, gymnastics or figure skating, have a higher risk of becoming anorexic. Male jockeys and wrestlers who must stringently watch their weight are also at increased risk.
More recently, researchers have found evidence that a proclivity to anorexia may be genetic. A large study of female twins published in Archives of General Psychiatry last year found that identical twins were more likely to share the disorder. The study concluded that 60% of the risk of developing anorexia was linked to heredity and the remaining risk was related to social factors.
