Bulimia Nervosa

Epidemiology

In women, the full syndrome of BN occurs with a lifetime prevalence of 1 to 3%. Variants of the disorder, such as occasional binge eating or purging, are much more common and occur in 5 to 10% of young women. The frequency of BN among men is less than one-tenth of that among women. The prevalence of BN increased dramatically in the early 1970s and 1980s but may have leveled off or declined somewhat in recent years.

Etiology

As with AN, the etiology of BN is likely to be multifactorial. Patients who develop BN describe a higher-than-expected prevalence of childhood and parental obesity, suggesting that a predisposition towards obesity may increase vulnerability to this eating disorder. The marked increase in the number of cases of BN during the past 25 years and the rarity of BN in underdeveloped countries suggest that cultural factors are important. Several biologic abnormalities in patients with BN may perpetuate this disorder once it has begun. These include abnormalities of CNS serotonergic function, which is involved in the regulation of eating behavior, and disruption of peripheral satiety mechanisms, including the release of cholecystokinin (CCK) from the small intestine.

Clinical Features

Table 65-3.

The typical patient presenting for treatment of BN is a woman of normal weight in her mid-twenties who reports binge eating and purging 5 to 10 times a week for 5 to 10 years. The disorder usually begins in late adolescence or early adulthood during or following a diet, often in association with depressed mood. The self-imposed caloric restriction leads to increased hunger and to overeating. In an attempt to avoid weight gain, the patient induces vomiting, takes laxatives or diuretics, or engages in some other form of compensatory behavior. During binges, patients with this disorder tend to consume large amounts of sweet foods with a high fat content, such as dessert items. The most frequent compensatory behaviors are self-induced vomiting and laxative abuse, but a wide variety of techniques have been described, including the omission of insulin injections by individuals with type 1 diabetes mellitus. Initially, patients may experience a sense of satisfaction that appealing food can be eaten without weight gain. However, as the disorder progresses, patients perceive diminished control over eating. Binges increase in size and frequency and are provoked by a variety of stimuli, such as transient depression, anxiety, or a sense that too much food has been consumed in a normal meal. Between binges, patients attempt to restrict caloric intake, which increases hunger and sets the stage for the next binge. Typically, patients with BN are ashamed of their behavior and endeavor to keep their disorder hidden from family and friends. Like patients with AN, those with BN place an unusual emphasis on weight and shape as a basis for their self-esteem. Many patients with BN have mild symptoms of depression. Some patients exhibit serious mood and behavioral disturbances, such as suicide attempts, sexual promiscuity, and drug and alcohol abuse. Although vomiting may be triggered initially by manual stimulation of the gag reflex, most patients with BN develop the ability to induce vomiting at will. Rarely, patients resort to the regular use of syrup of ipecac. Laxatives and diuretics are frequently taken in impressive quantities, such as 30 or 60 laxative pills on a single occasion. The resulting fluid loss produces dehydration and a feeling of emptiness but has little impact on caloric balance.