Study leader Dr. Walter Kaye -- professor of psychiatry and director of the Eating Disorder Treatment and Research Program at the University of California, San Diego, School of Medicine -- used a brain imaging technology, positron emission tomography, that permits visualization of dopamine function in the brain.
To provoke dopamine levels in the brain, the scientists administered a one-time dose of the drug amphetamine, which releases dopamine in the brain.
The study, published in the International Journal of Eating Disorders, says the amphetamine-induced release of dopamine in healthy women without an eating disorder was associated with feelings of extreme pleasure in the part of the "reward" center of the brain. However, amphetamine made those with anorexia nervosa feel anxious, and the part of the brain activated was the part that worries about consequences.
"This is the first study to demonstrate a biological reason why individuals with anorexia nervosa have a paradoxical response to food," Kaye says in a statement. "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."