The prevalence of AN is approximately 0.5% to 1% and is highest among adolescent girls and young women. Anorexia nervosa is characterized by an abnormally low body weight (at least 15% below what would be expected), a corresponding fear of weight gain, and an undue emphasis on weight and shape in self-evaluation.
5 Although amenorrhea (ie, loss of 3 consecutive menstrual cycles) is currently required for the diagnosis, the importance of this symptom is unclear, and as such, the eating disorders workgroup of the
Diagnostic and Statistical Manual of Mental Disorders (DSM) (Fifth Edition) has strongly considered removing it as a criterion for AN.
6 Anorexia nervosa can be classified into 2 subtypes: the restricting subtype and the binge-eating/purging subtype. Patients with AN who rarely binge-eat or purge but maintain a fairly regular pattern of caloric restriction may be classified as having the restricting subtype, whereas those who regularly engage in binge eating and/or compensatory behavior to prevent weight gain will be diagnosed as having the binge-eating/purging subtype.
5 Many of those with the restricting subtype will eventually develop binge eating, with at least one-third of patients crossing over into BN.
11 Crossover to binge eating and BN typically occurs within the first 5 years of the illness.
11 Women with AN who develop BN are likely to relapse back into AN.
11The outcomes associated with AN are poor, with only a 35% to 85% recovery rate and a protracted recovery, ranging from 57 to 79 months.
12 Not only can AN evolve into a chronic condition, it is one of the most medically serious psychiatric disorders.
13,14 People with AN are affected by the physical consequences of the severe weight loss, along
with psychological comorbid conditions that contribute to mortality,
15 with suicides representing a large portion of the deaths from AN.
14 Depression, a consequence of poor caloric intake and low weight, is frequently comorbid with AN and often resolves with refeeding.
16 Anxiety symptoms are common and often precede the development of the illness.
17The emaciated patient requires urgent medical attention, with close monitoring for dehydration, electrolyte disturbances, renal problems, cardiac compromise with a variety of arrhythmias, and refeeding syndrome. Hypomagnesemia may underlie hypokalemia that persists despite replacement. Metabolic alkalosis is the most common acid-base disturbance in patients with eating disorders, particularly those who purge by vomiting. Rapid development of hypophosphatemia during refeeding may herald refeeding syndrome, characterized by rapid shifts in fluids and electrolytes, including hypomagnesemia, hypokalemia, gastric dilation, and severe edema. Although relatively rare, this syndrome may even result in delirium, cardiac arrhythmia, coma, and death.
18 Gradual initial refeeding of the severely underweight patient can help prevent refeeding syndrome. Phosphorus supplementation should be initiated early, and phosphorus levels should be sustained above 3.0 mg/dL (to convert to mmol/L, multiply by 0.323). Patients should be monitored daily for hypophosphatemia, hypomagnesemia, hypokalemia, and other electrolyte disturbances, with treatment as needed. Accordingly, inpatient treatment may be indicated in patients who are less than 70% of ideal body weight or when low weight is accompanied by bradycardia, hypotension, hypoglycemia, hypokalemia, or hypophosphatemia.
The negative effect of AN on patients' long-term physical health is well established. Given that AN most commonly affects women during the period of development of peak bone mass, the effects on bone can be severe and debilitating.
13,19 Although estrogen preparations, mostly oral contraceptives, are widely prescribed to women with AN for the purpose of ameliorating bone loss, little evidence supports its use.
20-22 Not only do estrogen preparations provide questionable benefit, they also present some disadvantages to women with AN.
21 Once oral contraceptives reestablish menses, the clinician's ability to discern when a healthy weight has been reached, signaled by resumption of menses, becomes disrupted, and an important source of motivation for weight restoration is lost to the patient.
21Although the format has not been systematically investigated, practice guidelines for the treatment of AN recommend a multidisciplinary approach involving medical management, nutritional intervention, and psychotherapy.
23 The research literature is limited by small trials and lack of randomized trials. A recent meta-analysis of psychotherapies found that no specific psychotherapy was consistently superior to any other approach. However, for children and adolescents, a family-based approach for the treatment of eating disorders has demonstrated positive outcomes for adolescents with early onset and relatively short histories of AN.
24-27 This approach entails a specific form of family therapy in which the family is enlisted as a resource in the treatment of the patient.
27Although selective serotonin reuptake inhibitors are frequently prescribed for AN, most placebo-controlled trials have not found evidence that these medications improve weight gain, eating disorders, or associated psychopathology. Moreover, a recent study found no differences in the time to relapse between weight-restored patients with AN who were randomized to fluoxetine and those receiving placebo.
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