Teenagers with different eating disorders, such as anorexia nervosa and bulimia nervosa, can be distinguished by different patterns of activity in their brains, according to a new study.

The results show that the brain activity patterns of patients match up with aspects of their personality and behavior that often go hand-in-hand with their disorders. For example, patients with bulimia, who binge eat and then purge, tend to be more impulsive and risk-seeking, and report engaging in spontaneous behaviors such as shoplifting. Patients with anorexia , on the other hand, who restrict their food intake, tend to be more inhibited and anxious.

Despite some similarities among patients with distinct eating disorders, differences exist at the brain level, the researchers said. Therapies for these disorders may be more effective if they were geared toward specific traits, such as anxiety in anorexics and impulsively in bulimics.

The study was published in the January issue of the American Journal of Psychiatry.

The study involved 16 patients with anorexia, 15 with bulimia and 16 without an eating disorder. The average age of anorexia patients and healthy individuals was 15 years old, and the average age of bulimics was 17 years old.

The researchers scanned the patients' brains using functional magnetic resonance imaging (fMRI) while the patients performed a specific task designed to measure their ability to inhibit their responses to specific cues. The participants saw a series of letters and were told to press a button every time they saw a letter, except in the case of the letter X. When the letter X came up, they had to restrain from pushing the button.

The patients with bulimia had to use more brain power to stop themselves from pushing the button when they saw the letter X than did those with anorexia or the healthy participants, said study researcher James Lock, a professor of psychiatry and behavioral sciences at Stanford University.

"It took more parts of the brain, with greater levels of activation in the brain, to inhibit the responses to the same level as the anorexics," Lock told MyHealthNewsDaily.

However, some experts are skeptical of the new findings. Rachel Marsh, an assistant professor of clinical psychology at Columbia University in New York, published a study in 2009 that showed that adults with bulimia actually had less activity in some of these same brain areas than healthy adults when they performed a similar task. She and her colleagues concluded the decreased brain activity in bulimia patients meant these particular brain regions were not functioning optimally compared with those of healthy adults.

Essentially, these two studies drew the same conclusion from opposite findings.

"I have trouble understanding the discrepancy between these findings and ours," Marsh said.

Marsh noted that, in the new study, patients with bulimia had symptoms that were not as severe as the patients in her study. And in the new study, some patients with anorexia who also binged and purged were included in the same group as the bulimic patients. "Those two disorders are quite, quite different," Marsh said.

The number of participants in the new study was also quite small, which may explain why the researchers did not find specific brain activity patterns associated with the way patients with anorexia performed on the task.

A better understanding of the abnormal brain circuits in patients with eating disorders may help researchers find ways to target these circuits with therapy, Marsh said.

Because the adolescents in the new study had had their eating disorder for a relatively short period of time, the findings suggest these brain activity patterns may be a risk factor for an eating disorder, rather than a result of it, Lock said.

Pass it on: It may take more brain power for patients with bulimia to inhibit their responses to specific cues. This brain activity pattern agrees with the impulsive behavior often seen in bulimia.

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