Generalized sensitization of brain-reward responsiveness may last long into recovery.
Even after undergoing weeks of treatment for anorexia nervosa, patients still need time for their brains to normalize, according to a study.
Investigators examined 21 female adolescents before and after treatment for anorexia. The results of the study, published in theAmerican Journal of Psychiatry, found that the patients’ brains still had an elevated reward system compared to their counterparts without the eating disorder.
“That means they are not cured,” said senior author Guido Frank, MD. “This disease fundamentally changes the brain response to stimuli in our environment. The brain has to normalize and that takes time.”
Brain scans of patients with anorexia have implicated central reward circuits that govern appetite and food intake in the disease. In the current study, investigators demonstrated that the reward system became elevated when the individuals were underweight, but remained that way even after the weight was restored.
The investigators believe that dopamine may be the key because it mediates reward learning and is suspected of playing a significant role in the pathology of anorexia nervosa. Prior studies using animals have shown that weight loss or food restriction elevates dopamine response to rewards.
Using this knowledge, the investigators sought to determine if the heightened brain activity would normalize once a patient’s weight was restored. The participants, ages 15 to 16 years, underwent a series of reward-learning taste tests during brain scans.
The results of the study showed that the reward responses were higher in participants with anorexia compared with those without the disease. Although it somewhat normalized after weight gain, it remained elevated.
Furthermore, the study revealed that patients with anorexia had widespread changes to parts of the brain, such as the insula, which processes functions like taste and body self-awareness.
The more severely the brain was altered, the harder it was to treat anorexia. Meaning the more severely altered the brain was, the more difficult it was for patients to gain weight during treatment, according to the authors.
“Generalized sensation of brain reward responsiveness may last long into recover,” the authors wrote. “Whether individuals with anorexia nervosa have a genetic predisposition for such sensitization requires further study.”
To determine if the continuous elevated brain response is due to heightened dopamine reaction to starvation and whether it signals a severe form of anorexia among more treatment-resistant adolescents will require more research.
Regardless, the authors said the discovered biological markers could be used to determine the likelihood of treatment success. It could also push research toward using drugs that target the dopamine reward system.
“Anorexia nervosa is hard to treat,” Dr Frank said. “It is the third most common chronic illness among teenage girls with a mortality rate 12 times higher than the death rate for all causes of death for females 15 to 24 years old. But with studies like this we are learning more and more about what is actually happening in the brain. And if we understand the system, we can develop better strategies to treat the disease.”