Psychiatric Comorbidity
There is a high association of affective disorders with bulimia nervosa, with lifetime rates of over 80%. Major depression is most common, occurring in one-third of patients with bulimia nervosa and more than one-half of patients with mixed bulimia nervosa and anorexia nervosa. Depression may precede, follow, or coincide with bulimia. Studies suggest that depression and bulimia operate independently, although both tend to improve with treatment. Anxiety disorders including generalized anxiety disorder, panic disorder, obsessive-compulsive disorder, social phobia, and posttraumatic stress disorder occur in nearly 60% of cases. Patients with bulimia nervosa also have a significant lifetime risk for alcohol and substance abuse, which may be concurrent with their eating disorder.

Personality disorders are commonly associated with bulimia nervosa, with rates ranging from 22% to 77% in published studies. Cluster B (dramatic) personality disorders including borderline personality disorder are most common, but Cluster C (anxious) personality disorders, including avoidant personality disorder, are frequently diagnosed.

Medical Complications
The most serious medical complications of bulimia nervosa are caused by the cardiovascular effects of fluid and electrolyte imbalance. Purging behavior, including vomiting and laxative and diuretic abuse, may cause life-threatening cardiac arrhythmias. Orthostatic hypotension associated with light-headedness and dizziness; headaches, insomnia, and fatigue; dental caries and erosion of tooth enamel; and gastritis and esophagitis are common. Benign enlargement of the parotid and salivary glands occurs in about 25% of patients. The presence of a skin lesion on the back of the hand is a frequent sign of active behavior. In addition to hypokalemia, blood tests may show hypomagnesemia, disturbances in acid-base balance, and elevated serum amylase. Electrocardiogram changes such as ST segment depression and U waves may occur. Cardiomyopathy from emetine poisoning may develop in patients who use ipecac syrup to induce vomiting and may result in death. Patients who use baking soda to induce vomiting are at risk for developing life-threatening acid-base imbalance. Patients with bulimia nervosa are at increased risk for developing seizures. They may have irregular menses or be amenorrheic.

Natural History
Bulimia typically begins in adolescence or young adulthood in individuals consciously trying to stay slim. Some report a history of anorexia nervosa and others report a history of obesity. The onset often follows changes in living situations such as leaving home, starting college, changing jobs, or becoming involved in new relationships.

The course is usually chronic, and patients often engage in such behavior for years before seeking treatment. The chronicity of the illness may be punctuated by brief remissions in which the behavior is absent or the frequency and severity of the symptoms are reduced. Many report experiencing periods of relative improvement and other periods of worsening symptoms.