Anorexia nervosa
307.1 Anorexia Nervosa
Diagnostic Features
The essential features of Anorexia Nervosa are that the individual refuses to maintain a minimally normal body weight, is intensely afraid of gaining weight, and exhibits a significant disturbance in the perception of the shape or size of his or her body. In addition, postmenarcheal females with this disorder are amenorrheic. (The term anorexia is a misnomer because loss of appetite is rare.)
The individual maintains a body weight that is below a minimally normal level for age and height (Criterion A). When Anorexia Nervosa develops in an individual during childhood or early adolescence, there may be failure to make expected weight gains (i.e., while growing in height) instead of weight loss.
Criterion A provides a guideline for determining when the individual meets the threshold for being underweight. It suggests that the individual weigh less than 85% of that weight that is considered normal for that person's age and height (usually computed using one of several published versions of the Metropolitan Life Insurance tables or pediatric growth charts). An alternative and somewhat stricter guideline (used in the ICD-10 Diagnostic Criteria for Research) requires that the individual have a body mass index (BMI) (calculated as weight in kilograms/height in meters2) equal to or below 17.5 kg/m2. These cutoffs are provided only as suggested guidelines for the clinician, since it is unreasonable to specify a single standard for minimally normal weight that applies to all individuals of a given age and height. In determining a minimally normal weight, the clinician should consider not only such guidelines but also the individual's body build and weight history.
Usually weight loss is accomplished primarily through reduction in total food intake. Although individuals may begin by excluding from their diet what they perceive to be highly caloric foods, most eventually end up with a very restricted diet that is sometimes limited to only a few foods. Additional methods of weight loss include purging (i.e., self-induced vomiting or the misuse of laxatives or diuretics) and increased or excessive exercise.
Individuals with this disorder intensely fear gaining weight or becoming fat (Criterion B). This intense fear of becoming fat is usually not alleviated by the weight loss. In fact, concern about weight gain often increases even as actual weight continues to decrease.
The experience and significance of body weight and shape are distorted in these individuals (Criterion C). Some individuals feel globally overweight. Others realize that they are thin but are still concerned that certain parts of their bodies, particularly the abdomen, buttocks, and thighs, are "too fat." They may employ a wide variety of techniques to estimate their body size or weight, including excessive weighing, obsessive measuring of body parts, and persistently using a mirror to check for perceived areas of "fat." The self-esteem of individuals with Anorexia Nervosa is highly dependent on their body shape and weight. Weight loss is viewed as an impressive achievement and a sign of extraordinary self-discipline, whereas weight gain is perceived as an unacceptable failure of self-control. Though some individuals with this disorder may acknowledge being thin, they typically deny the serious medical implications of their malnourished state.
In postmenarcheal females, amenorrhea (due to abnormally low levels of estrogen secretion that are due in turn to diminished pituitary secretion of follicle-stimulating hormone [FSH] and luteinizing hormone [LH]) is an indicator of physiological dysfunction in Anorexia Nervosa (Criterion D). Amenorrhea is usually a consequence of the weight loss but, in a minority of individuals, may actually precede it. In prepubertal females, menarche may be delayed by the illness.
The individual is often brought to professional attention by family members after marked weight loss (or failure to make expected weight gains) has occurred. If individuals seek help on their own, it is usually because of their subjective distress over the somatic and psychological sequelae of starvation. It is rare for an individual with Anorexia Nervosa to complain of weight loss per se. Individuals with Anorexia Nervosa frequently lack insight into, or have considerable denial of, the problem and may be unreliable historians. It is therefore often necessary to obtain information from parents or other outside sources to evaluate the degree of weight loss and other features of the illness.
Subtypes
The following subtypes can be used to specify the presence or absence of regular binge eating or purging during the current episode of Anorexia Nervosa:
- Restricting Type. This subtype describes presentations in which weight loss is accomplished primarily through dieting, fasting, or excessive exercise. During the current episode, these individuals have not regularly engaged in binge eating or purging.
- Binge-Eating/Purging Type. This subtype is used when the individual has regularly engaged in binge eating or purging (or both) during the current episode. Most individuals with Anorexia Nervosa who binge eat also purge through self-induced vomiting or the misuse of laxatives, diuretics, or enemas. Some individuals included in this subtype do not binge eat, but do regularly purge after the consumption of small amounts of food. It appears that most individuals with Binge-Eating/Purging Type engage in these behaviors at least weekly, but sufficient information is not available to justify the specification of a minimum frequency.
Associated Features and Disorders
Associated descriptive features and mental disorders.
When seriously underweight, many individuals with Anorexia Nervosa manifest depressive symptoms such as depressed mood, social withdrawal, irritability, insomnia, and diminished interest in sex. Such individuals may have symptomatic presentations that meet criteria for Major Depressive Disorder. Because these features are also observed in individuals without Anorexia Nervosa who are undergoing starvation, many of the depressive features may be secondary to the physiological sequelae of semistarvation. Symptoms of mood disturbance must therefore be reassessed after partial or complete weight restoration.
Obsessive-compulsive features, both related and unrelated to food, are often prominent. Most individuals with Anorexia Nervosa are preoccupied with thoughts of food. Some collect recipes or hoard food. Observations of behaviors associated with other forms of starvation suggest that obsessions and compulsions related to food may be caused or exacerbated by undernutrition. When individuals with Anorexia Nervosa exhibit obsessions and compulsions that are not related to food, body shape, or weight, an additional diagnosis of Obsessive-Compulsive Disorder may be warranted.
Other features sometimes associated with Anorexia Nervosa include concerns about eating in public, feelings of ineffectiveness, a strong need to control one's environment, inflexible thinking, limited social spontaneity, perfectionism, and overly restrained initiative and emotional expression. A substantial portion of individuals with Anorexia Nervosa have a personality disturbance that meets criteria for at least one Personality Disorder. Compared with individuals with Anorexia Nervosa, Restricting Type, those with the Binge-Eating/Purging Type are more likely to have other impulse-control problems, to abuse alcohol or other drugs, to exhibit more mood lability, to be sexually active, to have a greater frequency of suicide attempts in their history, and to have a personality disturbance that meets criteria for Borderline Personality Disorder.
Associated laboratory findings.
Although some individuals with Anorexia Nervosa exhibit no laboratory abnormalities, the semistarvation characteristic of this disorder can affect most major organ systems and produce a variety of disturbances. The induced vomiting and abuse of laxatives, diuretics, and enemas can also cause a number of disturbances leading to abnormal laboratory findings.
Hematology: Leukopenia and mild anemia are common; thrombocytopenia occurs rarely.
Chemistry: Dehydration may be reflected by an elevated blood urea nitrogen (BUN). Hypercholesterolemia is common. Liver function tests may be elevated. Hypomagnesemia, hypozincemia, hypophosphatemia, and hyperamylasemia are occasionally found. Induced vomiting may lead to metabolic alkalosis (elevated serum bicarbonate), hypochloremia, and hypokalemia, and laxative abuse may cause a metabolic acidosis. Serum thyroxine (T4) levels are usually in the low-normal range; triiodothyronine (T3) levels are decreased. Hyperadrenocorticism and abnormal responsiveness to a variety of neuroendocrine challenges are common.
In females, low serum estrogen levels are present, whereas males have low levels of serum testosterone. There is a regression of the hypothalamic-pituitary-gonadal axis in both sexes in that the 24-hour pattern of secretion of luteinizing hormone (LH) resembles that normally seen in prepubertal or pubertal individuals.
Electrocardiography: Sinus bradycardia and, rarely, arrhythmias are observed.
Electroencephalography: Diffuse abnormalities, reflecting a metabolic encephalopathy, may result from significant fluid and electrolyte disturbances.
Brain imaging: An increase in the ventricular-brain ratio secondary to starvation is often seen.
Resting energy expenditure: This is often significantly reduced.
Associated physical examination findings and general medical conditions.
Many of the physical signs and symptoms of Anorexia Nervosa are attributable to starvation. In addition to amenorrhea, there may be complaints of constipation, abdominal pain, cold intolerance, lethargy, and excess energy. The most obvious finding on physical examination is emaciation. There may also be significant hypotension, hypothermia, and dryness of skin. Some individuals develop lanugo, a fine downy body hair, on their trunks. Most individuals with Anorexia Nervosa exhibit bradycardia. Some develop peripheral edema, especially during weight restoration or on cessation of laxative and diuretic abuse. Rarely, petechiae, usually on the extremities, may indicate a bleeding diathesis. Some individuals evidence a yellowing of the skin associated with hypercarotenemia. Hypertrophy of the salivary glands, particularly the parotid glands, may be present. Individuals who induce vomiting may have dental enamel erosion and some may have scars or calluses on the dorsum of the hand from contact with the teeth when using the hand to induce vomiting.
The semistarvation of Anorexia Nervosa, and the purging behaviors sometimes associated with it, can result in significant associated general medical conditions. These include the development of normochromic normocytic anemia, impaired renal function (associated with chronic dehydration and hypokalemia), cardiovascular problems (severe hypotension, arrhythmias), dental problems, and osteoporosis (resulting from low calcium intake and absorption, reduced estrogen secretion, and increased cortisol secretion).
Specific Culture, Age, and Gender Features
Anorexia Nervosa appears to be far more prevalent in industrialized societies, in which there is an abundance of food and in which, especially for females, being considered attractive is linked to being thin. The disorder is probably most common in the United States, Canada, Europe, Australia, Japan, New Zealand, and South Africa, but little systematic work has examined prevalence in other cultures. Immigrants from cultures in which the disorder is rare who emigrate to cultures in which the disorder is more prevalent may develop Anorexia Nervosa as thin-body ideals are assimilated. Cultural factors may also influence the manifestations of the disorder. For example, in some cultures, disturbed perception of the body or fear of weight gain may not be prominent and the expressed motivation for food restriction may have a different content, such as epigastric discomfort or distaste for food.
Anorexia Nervosa rarely begins before puberty, but there are suggestions that the severity of associated mental disturbances may be greater among prepubertal individuals who develop the illness. However, data also suggest that when the illness begins during early adolescence (between ages 13 and 18 years), it may be associated with a better prognosis. More than 90% of cases of Anorexia Nervosa occur in females.
Prevalence
The lifetime prevalence of Anorexia Nervosa among females is approximately 0.5%. Individuals who are subthreshold for the disorder (i.e., with Eating Disorder Not Otherwise Specified) are more commonly encountered. The prevalence of Anorexia Nervosa among males is approximately one-tenth that among females. The incidence of Anorexia Nervosa appears to have increased in recent decades.
Course
Anorexia Nervosa typically begins in mid- to late adolescence (age 14-18 years). The onset of this disorder rarely occurs in females over age 40 years. The onset of illness may be associated with a stressful life event. The course and outcome of Anorexia Nervosa are highly variable. Some individuals with Anorexia Nervosa recover fully after a single episode, some exhibit a fluctuating pattern of weight gain followed by relapse, and others experience a chronically deteriorating course of the illness over many years. With time, particularly within the first 5 years of onset, a significant fraction of individuals with the Restricting Type of Anorexia Nervosa develop binge eating, indicating a change to the Binge Eating/Purging subtype. A sustained shift in clinical presentation (e.g., weight gain plus the presence of binge eating and purging) may eventually warrant a change in diagnosis to Bulimia Nervosa.
Hospitalization may be required to restore weight and to address fluid and electrolyte imbalances. Of individuals admitted to university hospitals, the long-term mortality from Anorexia Nervosa is over 10%. Death most commonly results from starvation, suicide, or electrolyte imbalance.
Familial Pattern
There is an increased risk of Anorexia Nervosa among first-degree biological relatives of individuals with the disorder. An increased risk of Mood Disorders has also been found among first-degree biological relatives of individuals with Anorexia Nervosa, particularly relatives of individuals with the Binge-Eating/Purging Type. Studies of Anorexia Nervosa in twins have found concordance rates for monozygotic twins to be significantly higher than those for dizygotic twins.
Differential Diagnosis
Other possible causes of significant weight loss should be considered in the differential diagnosis of Anorexia Nervosa, especially when the presenting features are atypical (such as an onset of illness after age 40 years). In general medical conditions (e.g., gastrointestinal disease, brain tumors, occult malignancies, and acquired immunodeficiency syndrome [AIDS]), serious weight loss may occur, but individuals with such disorders usually do not have a distorted body image and a desire for further weight loss. The superior mesenteric artery syndrome (characterized by postprandial vomiting secondary to intermittent gastric outlet obstruction) should be distinguished from Anorexia Nervosa, although this syndrome may sometimes develop in individuals with Anorexia Nervosa because of their emaciation. In Major Depressive Disorder, severe weight loss may occur, but most individuals with Major Depressive Disorder do not have a desire for excessive weight loss or excessive fear of gaining weight. In Schizophrenia, individuals may exhibit odd eating behavior and occasionally experience significant weight loss, but they rarely show the fear of gaining weight and the body image disturbance required for a diagnosis of Anorexia Nervosa.
Some of the features of Anorexia Nervosa are part of the criteria sets for Social Phobia, Obsessive-Compulsive Disorder, and Body Dysmorphic Disorder. Specifically, individuals may be humiliated or embarrassed to be seen eating in public, as in Social Phobia; may exhibit obsessions and compulsions related to food, as in Obsessive-Compulsive Disorder; or may be preoccupied with an imagined defect in bodily appearance, as in Body Dysmorphic Disorder. If the individual with Anorexia Nervosa has social fears that are limited to eating behavior alone, the diagnosis of Social Phobia should not be made, but social fears unrelated to eating behavior (e.g., excessive fear of speaking in public) may warrant an additional diagnosis of Social Phobia. Similarly, an additional diagnosis of Obsessive-Compulsive Disorder should be considered only if the individual exhibits obsessions and compulsions unrelated to food (e.g., an excessive fear of contamination), and an additional diagnosis of Body Dysmorphic Disorder should be considered only if the distortion is unrelated to body shape and size (e.g., preoccupation that one's nose is too big).
In Bulimia Nervosa, individuals exhibit recurrent episodes of binge eating, engage in inappropriate behavior to avoid weight gain (e.g., self-induced vomiting), and are overly concerned with body shape and weight. However, unlike individuals with Anorexia Nervosa, Binge-Eating/Purging Type, individuals with Bulimia Nervosa are able to maintain body weight at or above a minimally normal level.
Diagnostic criteria for 307.1 Anorexia Nervosa
- Refusal to maintain body weight at or above a minimally normal weight for age and height (e.g., weight loss leading to maintenance of body weight less than 85% of that expected; or failure to make expected weight gain during period of growth, leading to body weight less than 85% of that expected).
- Intense fear of gaining weight or becoming fat, even though underweight.
- Disturbance in the way in which one's body weight or shape is experienced, undue influence of body weight or shape on self-evaluation, or denial of the seriousness of the current low body weight.
- In postmenarcheal females, amenorrhea, i.e., the absence of at least three consecutive menstrual cycles. (A woman is considered to have amenorrhea if her periods occur only following hormone, e.g., estrogen, administration.)
Specify type:
- Restricting Type: during the current episode of Anorexia Nervosa, the person has not regularly engaged in binge-eating or purging behavior (i.e., self-induced vomiting or the misuse of laxatives, diuretics, or enemas)
- Binge-Eating/Purging Type: during the current episode of Anorexia Nervosa, the person has regularly engaged in binge-eating or purging behavior (i.e., self-induced vomiting or the misuse of laxatives, diuretics, or enemas)