Women’s risk for anorexia linked to genes

By Erin Lucero
Office of Development, School of Medicine

Genes significantly influence an individual’s risk for anorexia nervosa, according to the first population-based study to estimate the extent to which the eating disorder is linked to genetic make-up. The study also found a genetic correlation between anorexia and major depression.

The Virginia Commonwealth University study was published in the March issue of the American Journal of Psychiatry.

"Past research has shown that about 50 percent of women with anorexia also have lifetime depression, but it doesn’t explain why these two disorders seem to go hand-in-hand in some individuals," said Cynthia Bulik, Ph.D., a study co-author and psychologist at VCU’s Virginia Institute for Psychiatric and Behavioral Genetics. "Our study shows that not only do genetics significantly influence a woman’s vulnerability for anorexia, genetics also help explain the connection between anorexia and depression."

The VCU study estimated that a woman’s susceptibility to anorexia is about 58 percent genetically influenced, and that the frequent co-occurrence of anorexia and depression might be due to shared genetic effects.

While there are genes specific to each condition, there also appear to be genes shared by both disorders. Bulik describes three sets of genes: one set increases an individual’s risk of developing both anorexia and depression, perhaps by influencing a particular trait that is common to both conditions; a second set influences vulnerability to anorexia, but not depression; and a third increases vulnerability to depression, but not anorexia. An individual’s genetic make-up may incorporate genes from any, all or none of these sets.

Bulik points out that environmental factors also play a role in determining whether an individual develops either disorder. Such influences might, in fact, act as triggers for the expression of the genes.

To determine the extent to which genes influence anorexia, depression and the connection between the two, VCU researchers interviewed 2,163 female twins from the population-based Virginia Twin Registry. By studying twins, researchers can analyze the extent to which a condition has a genetic tendency. If a disorder is more frequently seen in both members of an identical twin pair than a fraternal twin pair, it is likely to have a strong genetic component.

Both anorexia and depression are more common in women than in men. Estimates reveal that for every man with anorexia, 10 women are affected, and for every man with depression, two women are affected. About 1 percent of women are affected by anorexia. Different studies have reported varying rates – from 17 percent to 30 percent – for depression in women.

The Virginia Institute for Psychiatric and Behavioral Genetics studies the genetic and environmental basis of many psychiatric disorders as well as common health and behavioral problems. The Virginia Twin Registry is the precursor to the Mid-Atlantic Twin Registry, a database of 64,000 preschool, school age and adult twins born or living in the states of Virginia, North Carolina and South Carolina, and nearly 40,000 of their relatives.