BY JAMIE TALAN
March 7, 2006
Two new studies show that genetics may outweigh any environmental factors in producing the eating disorders involved in anorexia and bingeing.
"This is good news for patients and their families," said Dr. Cynthia Bulik of the University of North Carolina School of Medicine. In the latest issue of the Archives of General Psychiatry, Bulik and colleagues studied records from 30,000 Swedish twins, some with anorexia, and found that identical twins, who share identical genes, were more likely to share an eating problem compared with fraternal twins, who share half their genes, the same as non-twin siblings.
In this large sample, scientists figured out that genes were responsible for 56 percent of the cases of the potentially life-threatening condition. People with anorexia - about 10 out of every 1,000 women and 29 in every 1,000 men - have symptoms that include self-starving and an obsessional belief that they are fat.
Bulik and others are trying to identify genetic risk factors so that they can better solve this puzzling eating behavior.
"We have gone through far too much time blaming parents," said Bulik, who used a 30,000-person twin registry from Sweden to identify the strong genetic contribution. "People need to understand that they are fighting their biology" and not just a psychological need to be thin.
Once genes are identified, the hope is that scientists can develop drugs that work directly on these target genes.
In another study published in the same journal, a team of investigators at McLean Hospital, a Harvard affiliate, found a strong genetic contribution to binge-eating. Binge-eating is far more common than other eating disorders, involving around 2 to 5 percent of the population. As the name implies, these binges are characterized by compulsive, episodic eating of large amounts of food in a short period.
Dr. James Hudson, director of the biological psychiatry laboratory at McLean and an associate professor of psychiatry at Harvard Medical School, recruited 300 people, half with a history of binge eating, and then set out to interview their parents, children and siblings. They found that family members of binge-eaters were twice as likely to have a similar eating disorder than those without a such a history. And the relatives of binge eaters were more than twice as likely to be obese than people who don't share this eating behavior.
Binge eaters are themselves no more likely than non-binge eaters to be obese, Hudson said. They do share some other features, however: They have more mood disorders and are more impulsive.
"There is very likely a genetic component," Hudson said. Both Hudson and Bulik believe that preventions and treatments lie hidden in the mysteries of the unidentified genes. Bulik and her colleagues have identified two possible markers for genes associated with the brain's opiate-like and serotonin chemicals. Both chemicals regulate mood, behavior and pleasure.
In another study, Bulik found that people with anorexia say that starving themselves makes them calmer. Normally, hunger triggers anxiety.