Anorexia Nervosa

Anorexia nervosa (AN) is a severe psychiatric illness primarily characterized by a refusal to maintain a minimally normal body weight for age and height. The term anorexia originates from the Greek word orexis, meaning appetite. Therefore, anorexia nervosa translates literally as a “nervous loss of appetite.” Clinical descriptions of AN emerged in the medical literature in the 1870s when it was described by both Er-nest-Charles Lasègue and Sir William Gull. Although it is a serious illness, AN affects a small percentage of the population. Evidence from epidemiological studies indicates that the lifetime prevalence rate for AN is approximately 1 percent in the female population, while rates for men range between one-tenth and one-third of the rates for women.

The full range of symptoms necessary to diagnose AN are detailed in the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV). The first diagnostic criterion is a refusal to maintain a minimally normal body weight. DSM-IV suggests a guideline of weight loss below 85 percent of expected body weight. However, the International Classification of Mental and Behavioral Disorders, 10th edition, stipulates a more stringent weight threshold of a body mass index of 17.5 kg/m2 to diagnose AN. The use of varying weight criterion has generally led clinicians to diagnose a patient's low weight status in relation to age, weight history, and weight at which menses regularly occurs. It is the refusal to maintain a normal weight that distinguishes AN from bulimia nervosa, the other main eating disorder described in DSM-IV.

Beyond an obstinate pursuit of thinness, the second diagnostic criterion for individuals with AN is an intense fear of gaining weight or becoming fat, despite being underweight. To be diagnosed with AN, an individual must also experience the third criterion, which is a distorted perception of body shape or weight, an excessive influence of shape and weight on self-evalua-tion or denial of the seriousness of being underweight. Because many patients with AN often have extremely ambivalent feelings about seeking treatment, they may deny a fear of weight gain even though this denial is incongruent with their overt behaviors to avoid weight gain. The final diagnostic criterion for AN is amenorrhea, signified by the absence of at least three consecutive menstrual cycles in postmenarcheal females. The current utility of this diagnostic criterion is debatable because research has found few differences between individuals with AN who menstruate regularly and those with amenorrhea. While it may not be a useful diagnostic distinction, it remains an important physiological indicator of possible hypothalamic disturbances, osteoporosis, and/or infertility.

Once the diagnosis of AN has been reached, it may be further classified into two distinct subtypes. The restricting subtype captures those individuals who employ weight loss strategies such as calorie restriction, fasting, or excessive exercise. Individuals with AN who engage in behaviors such as binge eating and/or purging via self-induced vomiting or the abuse of laxatives, enemas, or diuretics are classified as binge/purge subtype. Individuals who fall into the latter category tend to exhibit more impulsive behaviors such as self-mutilation, suicide attempts, stealing, or alcohol and/or substance abuse.

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