The eating disorder bulimia nervosa may be caused, at least in part, by chemical changes to the brain, researchers have discovered.
Scientists have found that chemical changes that take place in the brains of sufferers persist even after recovery.
Writing in the Archives of General Psychiatry, study leader Professor Walter Kaye, of the University of Pittsburgh, said brain serotonin activity and mood in bulimics are known to alter when they binge and purge. Women with bulimia are also known to have an obsession with perfectionism.
Serotonin is a neurotransmitter that helps regulate mood. The study found that these alterations and symptoms persisted after recovery from bulimia nervosa, suggesting that they are not merely a consequence of abnormal eating behaviors.
Theoretically, altered serotonin activity could cause anxious and obsessive behaviors, affect the control of appetite and thus contribute to an increased susceptibility to bulimia nervosa.
Dr Kaye said: "The development of an eating disorder is often attributed to the effects of our cultural environment, such as the mass media, which places a heavy emphasis on slimness.
"But while all women are exposed to these cultural mores, only a small percentage develop an eating disorder. Our study may have identified a biological risk factor that plays a part in deciding who develops a disorder."
Dr Kaye said the research was important because it would help shift focus to the underlying causes of bulimia nervosa. This would help scientists to concentrate on developing better treatments, and ways to identify people at risk before the disorder occurs.
Bulimia nervosa affects about one to three per cent of women - most of whom are of normal body weight. The symptoms usually appear during adolescence, and involve bingeing and purging, either by vomiting or using laxatives.
Distorted body image
Women with the disease often have a distorted image of their bodies, changes in brain chemistry and psychiatric symptoms such as depression, anxiety, obsessive-compulsive disorder and alcohol or other substance abuse.
Though researchers know the symptoms and effects of bulimia, the exact causes of the disorder have yet to be uncovered.
Because malnutrition associated with eating disorders affects brain chemistry, Dr Kaye and his colleagues compared 31 healthy volunteer women to 30 women who had recovered from bulimia nervosa.
The women who had recovered were of normal body weight, had regular menstrual cycles and had not binged or purged for more than a year.
The researchers assessed the recovered bulimia nervosa participants for persistent behaviour disturbances and measured levels of the major metabolites of the neurotransmitters serotonin, dopamine and norepinephrine.
They also gave the participants a non-therapeutic drug, m-chlorophenylpiperazine (mCPP), that specifically affects the serotonin system and causes hormonal and behavioral responses.
Dr. Kaye's team found that, compared to the healthy volunteers, the recovered women had increased levels of the serotonin metabolite, more negative moods and obsessions with perfectionism and exactness.
The levels of the other brain chemicals, dopamine and norepinephrine, were normal in comparison.
In addition, the group of recovered bulimia nervosa women had a more extreme response to mCPP.
October 14th 1998
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Brain chemicals may cause bulimia (mCPP given to recovered bulimia sufferers)