"Although many women diet, relatively few develop the extreme weight loss and the clinical symptoms of anorexia nervosa. An underlying biological diathesis and temperament may place someone at risk for developing anorexia nervosa. Certain traits, such as negative affect, behavioral inhibition, compliance, high harm avoidance, and an obsessive concern with symmetry, exactness, and perfectionism, persist after recovery from anorexia nervosa. These persistent symptoms raise the possibility that such traits exist premorbidly and contribute to the pathogenesis of this disorder. Such traits could be associated with increased brain serotonin activity. After recovery, anorexics have increased levels of 5-HIAA, the major metabolite of serotonin, in the cerebrospinal fluid (CSF). Low CSF 5-HIAA levels have been associated with impulsive and aggressive behaviors, which are opposite to those typically found in anorexia nervosa. Increased serotonin activity could contribute to many behavioral symptoms, such as increased satiety. Moreover, recent data suggest that selective serotonin reuptake inhibitor (SSRI)-type medication improves outcome and prevents relapse in people with anorexia nervosa. These theoretical issues have important clinical implications in this era of diminished support for treatment of eating disorders. Anorexia nervosa, like other major psychiatric disorders, has contributory pathophysiology and can benefit from and deserves appropriate treatment resources."