By Jeremy Laurance, Health Editor
07 April 2005
The eating disorder anorexia nervosa could be caused by a brain dysfunction, rather than social pressures, a study shows.
Researchers at St George's Hospital in Tooting, south London, found sufferers have an abnormality in the blood flow to an area of the brain which affects body image. In results presented at an international conference in London, the researchers say this points to a biological cause for the condition.
More than a million people in Britain suffer from eating disorders which were thought to be caused by social and cultural pressures.
Bryan Lask, a professor of child and adolescent psychiatry at St George's who led the research, said finding a biol-ogical cause could change the way the condition was treated.
"The biological cause has been under-emphasised and the socio-cultural pressures have been over-emphasised," he said. "There has to be a biological contribution otherwise everyone would be anorexic, given the socio-cultural pressures in our society.
"I am not saying people are born anorexic ... But I am saying some people are born with a genetic pre-disposition to anorexia which makes it more likely to develop. If you live in a society which promotes thinness as the ideal, you are more likely to develop anorexia if you have the biological predisposition."
The researchers used brain imaging and neurological testing which revealed the abnormal blood flow. "There is a low blood flow in one specific part of the brain on one side," Professor Lask said. "It occurs only in people with anorexia and does not occur in people without anorexia."
Anorexia is defined as a body weight maintained at least 15 per cent below that expected for the individual's height and age and has the highest death rate of any psychiatric condition. There are 11 new cases of anorexia diagnosed per 100,000 population each year, 90 per cent of them women.
Professor Lask said the abnormal blood flow observed in the brain imaging studies was more likely to be a cause than an effect of weight loss.
"It is such a specific effect in only one part of the brain. If it were the result of starving yourself you would expect global changes round the brain. And it tends not to return to normal when weight is regained. That is why we think it is cause rather than effect."
The discovery could ultimately point the way to a new treatment for anorexia, Professor Lask said. "But that could be 10 to 20 years away. This has helped us explain the difficulty people with anorexia have in inhibiting tormenting thoughts. They become totally obsessed with the idea that they are fat and overweight. It will enable us to put our energy into trying to alter their thinking processes."
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