Reuters North American News Service, December 3rd, 2007
CHICAGO (Reuters) - The male half of opposite-sex
twins shares a similar risk as his sister of developing the
eating disorder anorexia later in life, a finding that
researchers said Monday suggests exposure in the womb to a
female sex hormone may be responsible.
No one knows why girls and women are 10 times more likely
than males to develop anorexia, which is a pathological fear of
becoming fat that can lead to self-starvation and even death.
Many experts cite psychological factors behind the
phenomenon such as low self-esteem and society's promotion of
thinness, especially for women.
About 11 million Americans suffer from anorexia or bulimia
nervosa, another eating disorder where binge eating is followed
by purging either by vomiting, laxative abuse, or compulsive
exercising.
In the study of 4,478 sets of fraternal, opposite-sex twins
born between 1935 and 1958 in Sweden, a similar number of
individuals of both genders were subsequently diagnosed with
anorexia nervosa.
The chances that both opposite-sex twins would develop
anorexia was about the same as the risk for women in the
general population, according to the study published in the
Archives of General Psychiatry.
Sets of male twins did not have any higher risk than men in
the general population.
"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," wrote study authors Marco Procopio of
the University of Sussex, Brighton, England, and Paul Marriott,
of the University of Waterloo, Ontario, Canada.
"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," they wrote.
(Reporting by Andrew Stern; editing by Michael Conlon and
Philip Barbara)
