United Press International
Sunday, August 11, 2002
Researchers Find Anorexia Gene United Press International - August 07, 2002 SYDNEY, Australia, Aug 07, 2002 (United Press International via COMTEX) -- Australian researchers announced they have discovered a genetic link to the dieting disorder anorexia nervosa, for the first time showing how a predisposition to the illness might be inherited in a large number of sufferers.
The researchers, from the Department of Psychological Medicine at Westmead Children's Hospital, focused on norepinephrine, a brain chemical involved in anxiety. In particular they studied a region of the norepinephrine transporter gene where they discovered a new chunk of DNA that came in two sizes -- one long and one short.
In DNA taken from anorexics and their parents in 101 Australian families, researchers found that of 62 parents with both the long and short form of the DNA, 42 had passed on the longer version to their anorexic offspring, while 20 passed on the shorter version. Individuals receiving the long form from their parents were twice as likely to develop anorexia nervosa, researchers said.
Lead clinician Kenneth Nunn told United Press International anorexics may be super-metabolizers of norepinephrine.
"When they go on a diet, these super-metabolisers with the longer form of DNA could use up their supplies too quickly and go into a negative spiral of norepinephrine depletion from which they cannot escape. Once they begin to shut down and eat less, they become even more depleted of norepinephrine," Nunn said.
Anorexia affects up to one in 200 young women in Australia and up to one in 2,000 men. It sometimes is fatal and typically is diagnosed when a person falls below 85 percent of normal body weight, has a distorted view of what he or she looks like and has a drive to be thin. Sufferers also are very anxious.
The gene may not be linked solely to anorexia, however, lead researcher Ruth Urwin told UPI.
"It may also be relevant to some forms of depression, anxiety and post-traumatic stress disorder," she said.
The discovery has immediate implications in treatment for anorexia nervosa, Nunn said.
"There's no silver bullet for anorexia nervosa," he said. "But it could be useful to treat patients with drugs that refuel their norepinephrine system, like venlafaxine and reboxetine, once their weight is restored."
Pierre Beumont, professor of psychiatry at the University of Sydney and a co-author of the study, said the gene variation discovery is further evidence that anorexia is a brain disease, not psychological in origin and under the control of the patient as often thought.
Urwin pointed out, however, the discovery does not discount the importance of life events also influencing a person's probability of developing anorexia. It is a point taken up by Kate Baggs, a clinical psychologist at the University of Sydney who runs a program specializing in eating disorders.
"I think it's really important to put the genetic work into the context of all the years of research into the link between culture and body image," she told UPI. "You just have to talk to sufferers to realize how important the media (are) in shaping their minds in terms of what they want to look like. So many of my patients say to me, if only I wasn't size 14 I could be successful, rich and desirable."
The study is published in the journal Molecular Psychiatry.
Copyright 2002 by United Press International.