For decades doctors believed patients with anorexia nervosa to have remarkable, if misguided, control to override basic desires like hunger. The classic anorexia patient -- a teen who is not fat but may be a few pounds overweight -- was seen as someone with a single-minded drive to diet and exercise at all costs.
Now an important new study, published in the journal Nature Neuroscience on Monday, proposes that the power of habit -- yes, the same neural mechanisms that make you eat a cookie each afternoon, drive the same route home even if there are many alternatives, and shop at Target each weekend -- may play a greater role in anorexia than people previously thought.
The team studied 21 patients hospitalized for anorexia at the New York State Psychiatric Institute/Columbia University Medical Center Eating Disorders Research Clinic and 21 healthy control subjects over two days. They carried out a variety of tests, including having participants rate foods on their healthiness and "tastiness" and asking them to eat whatever they wished from a buffet-style array of foods. As expected, the participants were less likely to choose fattier and higher-calorie foods.
While the participants were making their choices, the authors of the study had them undergo magnetic resonance imaging of their brains. They found that for those with anorexia a part of the brain called the dorsal striatum region showed increased activity.
That part of the brain has been theorized to play a major role in decision-making, motivation and rewards, as well as habit learning. Previous studies have shown associations between dopamine levels and drug abuse. One study provided evidence that dopamine in the dorsal striatum involved with craving may play a role in cocaine addiction and suggested that therapies aimed at inhibiting dopamine increases are likely to be therapeutically beneficial.
In the anorexia study, this suggests that participants, who were hospitalized in order to gain weight, may not be making reasoned choices about the food but instead may be choosing their food based on their past choices.
"[T]heir ability to alter their pattern of food choice is exceedingly poor and, given the opportunity, they continue to choose low-fat and low-calorie foods. Thus, anorexia nervosa provides a unique and compelling model of persistent maladaptive behavior," researchers Karin Foerde from the New York State Psychiatric Institute, Joanna Steinglass from Columbia, and their colleagues wrote.
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