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Eating Disorders: Understanding Anorexia Nervosa

Eating Disorders: Understanding Anorexia Nervosa

National Eating Disorder Awareness Week

Anorexia nervosa (AN) is a disorder with no proven treatment that is effective in reversing core symptoms, and it may have the highest mortality rate of any psychiatric illness. It is a very difficult disorder to treat, in part, because those with AN often lack motivation to engage in treatment. Many people in today’s society diet frequently and want to lose weight, but very few develop AN. Considerable evidence suggests that heritability contributes to the development of an eating disorder. It may be that genes code for certain temperament traits in childhood, such as perfectionism, anxiety, obsessiveness, that create a susceptibility for the development of AN during adolescence.

Recent studies offer new understanding of alterations of neural circuitry that may contribute to development of AN. In particular, findings from these studies suggest how individuals with AN can severely restrict their caloric intake for years. In contrast, most people have difficulty adhering to a diet for a long period of time, and experience a high rate of recidivism after they lose weight. How are individuals with AN able to ignore signals regarding hunger that otherwise motivate eating, even when they are severely emaciated?

Understanding such questions may lead to the development of more effective treatments targeted at the underlying mechanisms of the disorder. For example, future treatments could address the neural circuitry of reward and the modulation of salient stimuli, such as food, as well as the circuitry contributing to anxious temperament or self-awareness of body states.

Reward insensitivity
One reason that it is difficult to get persons with AN to gain and maintain weight is because little in life is more rewarding to them than starvation. Clinically, individuals with AN have long been noted to be anhedonic and ascetic, and able to sustain not only the self-denial of food but also most comforts and pleasures in life.1 Behavioral studies show that individuals with AN have an enhanced ability to delay reward (ie, show less reduction in the value of a monetary reward over time) compared to healthy cohorts and this ability to delay reward may help them to maintain persistent food restriction.2

Persons with AN may be unable to appreciate rewarding stimuli because they are preoccupied with consequences.3 Thus, an altered balance between reward and inhibition appears to be a hallmark of AN. In fact, a recent review showed that persons with AN tend to have low reward reactivity but a high sensitivity to punishment in both the ill and recovered states.4 Imaging data support this hypothesis and suggest that altered reward sensitivity and increased behavioral inhibition in AN are related to underactive limbic (reward) circuitry and overactive executive (inhibition) neural circuitry.5,6 Clinically, this bias is likely to interfere with motivation as well as the ability to learn from experience. That is, ill persons with AN tend to perceive their actions as incorrect or flawed and are highly sensitive to criticism, rather than being able to appropriately proportion reward and punishment in order to learn from experience.

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