Anorexia may be caused by change in brain chemical

Sep 7 2005

A new study has found that women who have had a certain type of anorexia nervosa show a change in the activity of a chemical in their brain that is widely associated with anxiety and other affective disorders, for as long as one year after recovery.

Anorexia nervosa is a disorder where the sufferer is obsessive in their pursuit of thinness and fear of being fat.

The condition falls into two subtypes; in one eating is severely restricted, while in the other restrictive eating is practised along with episodes of bulimia and/or binge eating.

According to previous research, changes in the brain chemical serotonin, which is involved in the communication between nerve cells, may contribute to the appetite alteration in anorexia nervosa, as well as playing a role in anxious, obsessional behaviors and extremes of impulse control.

Scientist Ursula F. Bailer, M.D., of the University of Pittsburgh School of Medicine, Pittsburgh, and her colleagues compared the activity of serotonin in women who had recovered from each of the two types of anorexia nervosa and a control group of healthy women using positron emission tomography (PET).

In the study the researchers injected a molecule that binds to a serotonin receptor, in much the same way that serotonin does into specific areas of the women's brains.

They then used PET scans to measure the extent of the molecule-receptor binding, which became a marker for alterations of serotonin neuronal activity.

Included in the study were thirteen women who had recovered from the restricting-type of the condition, 12 women with bulimia-type anorexia and 18 healthy women.

The researchers found an increased binding of this marker molecule in several brain regions in women who had recovered from bulimia-type anorexia but not in the restricting-type.

Only the women who had recovered restricting-type anorexia showed any correlation between core eating disorder symptoms and binding potential.

In these women receptor binding was correlated with a measure of anxiety called harm avoidance.

The team concluded that women with anorexia have a disturbance of serotonin neuronal systems that may cause anxiety.

They are uncertain whether these alterations are a 'scar' following cessation of low weight and malnutrition, or whether they predate the onset of the anorexia and persist after recovery.

To date there are no proven treatments for anorexia, and the illness has the highest mortality of any psychiatric disorder.

The findings may possibly encourage a better understanding of anorexia and new drug and psychological treatments.

The study is published in the September issue of Archives of General Psychiatry, one of the JAMA/Archives journals.