People who suffer from the eating disorder anorexia nervosa have a fear of gaining weight that causes them to avoid food in unhealthy ways. The disorder most often begins in adolescence or early adulthood and affects about 0.9% of women and 0.3% of men in the U.S. If untreated, the disorder can cause side effects that include brain damage, heart damage, multiple organ failure, and muscle wasting. What causes this serious disorder?


Scientists still don’t exactly know the cause of anorexia nervosa, but one clue is that a person is more likely to suffer from it if they have a family member who has an eating disorder, even if the family member has a different maladaptive eating pattern. Heredity appears to play some role in eating disorders.


Temperament can also be a clue to the cause of eating disorders. Many who people who suffer from anorexia, bulimia, or both shared these characteristics as children: They were anxious, achievement-oriented, perfectionistic, and obsessive.


The brain’s reward system, which the human body shares with many other species in the animal kingdom, functions in an atypical way in people diagnosed with anorexia. The neurotransmitter dopamine, for example, has been shown to be overactive in women with anorexia. When most people see a meal on the table, they react with anticipation. People with anorexia see a meal on the table and their brains release dopamine, causing their anxiety levels to rise. These people report feeling worried when they see food.


Structures of the brain are also altered in people with anorexia. A region of brain called the dorsal striatum, which has to do with habitual behaviors, is different in women with anorexia than in healthy women. (Most scientific studies of anorexia nervosa are done on female volunteers since the disorder affects more women than men.)


The right insula, a region of the brain that helps process bodily sensations including taste sensations, is also altered in the brain scans of anorexia patients. Visceral hypersensitivity, a condition in which the right insula is atypical and people have an unusually intense focus on sensations inside their own bodies, may be correlated with anorexia. The condition is thought to distract people from their other normal, daily activities and force them to focus on what’s going on inside their own bodies. Some researchers think anorexia might be a kind of maladaptive coping mechanism in which patients try to “mute” their internal body processes by restricting food.


Researchers are still not sure whether some of these biological differences in people with anorexia are characteristics that make people more likely to develop the condition or whether some of these are effects of the disorder. Better understanding of the causes of anorexia nervosa may someday lead to more effective treatment options.