May 23, 2011 09:41 GMT  ·  By

People suffering from a condition called anorexia nervosa say that not eating makes them feel the same type of pleasure that healthy individuals experience when they eat an enjoyable food. When sufferers do eat, they tend to report an increase in anxiety levels.

There are the conclusions of a new scientific study, which sought to gain more insight into the root causes of anorexia nervosa, an extremely dangerous medical condition that makes people starve themselves and avoid eating anything for days.

On the other hand, food refusal makes them feel better and less anxious, the team explains. Details of the work appear in the latest online issue of the esteemed International Journal of Eating Disorders.

In the research, experts at the University of California in San Diego (UCSD) School of Medicine provide insight into why symptoms such as these occur in the condition. The team here proposed that the neurotransmitter dopamine might be involved in this.

As such, they gave test participants a one-time does of amphetamine, a drug that stimulates the emission of dopamine. All test subjects then had their neural dopamine activities measured via an investigations technique called positron emission tomography (PET).

In test subjects who were deemed healthy before the trials, dopamine tended to elicit feelings of extreme pleasure in the reward center of the brain. The effect was reversed for anorexia patients.

Exposure to amphetamine-inducted dopamine made the latter feel more anxious than usual, and activated portions of their brain that past studies associated with worrying about consequences.

“This is the first study to demonstrate a biological reason why individuals with anorexia nervosa have a paradoxical response to food,” explains UCSD psychiatry professor Walter Kaye, MD.

He also holds an appointment as the director of the Eating Disorder Treatment and Research Program at the university's School of Medicine, PsychCentral reports.

“It’s possible that when people with anorexia nervosa eat, the related release of the neurotransmitter dopamine makes them anxious, rather than experiencing a normal feeling of reward,” the expert adds.

“It is understandable why it is so difficult to get people with anorexia to eat and gain weight, because food generates intensely uncomfortable feelings of anxiety,” he concludes.