Drive for leanness, anorexia nervosa, and overactivity: the missing link.

Anorexia nervosa (AN) is a psychiatric condition characterized by deliberate reduction of body weight. Some patients with AN exhibit overactivity that can worsen their state of malnutrition. Employing an evolutionary psychiatry line of inquiry, we propose that rigidity of thinking and overactivity are behavioral phenotypic changes in AN patients that are normal to tree-dwelling mammals, such as monkeys. Such behavior can lead to good functioning as ballet dancers and athletes but lead to certain disadvantages in other areas of modern life. The overactivity in AN, though under conscious control may be neurobehavioral and driven subconsciously by disordered cerebral neuropsychopharmacology.