Bulimia Nervosa

Clinical picture

• Patients are normal weight or slightly above and hide the illness for years; secrecy, shame and disappearing to the bathroom after meals are typical.
• Binges of 1000-2000 kcal within about 2 hours carry a subjective loss of control and usually follow a period of daytime dietary restriction.
• Compensation includes self-induced vomiting in roughly 80%, plus laxatives, diuretics, fasting, driven exercise or insulin omission in diabetes.
• Exam findings include parotid hypertrophy, Russell sign on the dorsum of the hand, lingual enamel erosion, palatal petechiae and reflux esophagitis.
• Mood lability, impulsivity, self-injury and substance use co-occur far more often than in anorexia nervosa, forming a multi-impulsive presentation.
• Weight can swing several kilograms within a week, and menstrual irregularity occurs in most patients without frank amenorrhea.

Criteria snapshot

• Requires recurrent binges with loss of control plus inappropriate compensatory behavior, each averaging at least once weekly for a minimum of 3 months.
• A binge is defined by an objectively large amount of food eaten within about 2 hours relative to context, not by the patient's subjective sense alone.
• Self-evaluation must be unduly influenced by body shape and weight, the core cognitive feature that bulimia nervosa shares with anorexia nervosa.
• The diagnosis is not made if the behavior occurs only during episodes of anorexia nervosa, since significantly low weight directs the AN diagnosis instead.
• Severity is graded by weekly compensatory episodes: mild 1-3, moderate 4-7, severe 8-13, and extreme at 14 or more per week.

Neurobiology

• Heritability estimates run 50-60%, with serotonergic vulnerability shown by reduced 5-HT transporter binding and sensitivity to tryptophan depletion.
• Blunted ventral striatal and anterior cingulate reward response combined with heightened orbitofrontal food cue reactivity underlies loss of control.
• Dieting lowers brain tryptophan and serotonin availability in women, which helps explain why binges are precipitated by restriction rather than hunger.
• Vomiting produces hypokalemic, hypochloremic metabolic alkalosis, whereas laxative abuse instead generates a hyperchloremic metabolic acidosis.
• Cardiac risk arises from hypokalemia and QTc prolongation, with rarer ipecac cardiomyopathy and Boerhaave syndrome esophageal rupture.
• Post-purge reflex hypoglycemia and rebound edema when purging stops drive early relapse unless anticipated and explained to the patient.

Psychology

• Restraint theory: rigid dietary rules create abstinence violation effects, so a single lapse escalates into a full binge and then compensatory purging.
• Purging is negatively reinforced by rapid anxiety relief, making it the most heavily operant-conditioned and treatment-resistant part of the cycle.
• The affect regulation model holds that bingeing narrows attention away from aversive self-awareness, and emotional escape predicts episode timing.
• High impulsivity, novelty seeking and rates of childhood maltreatment exceed those in anorexia and predict comorbid substance use and self-harm.
• Shape-based self-worth sustained by body checking and body avoidance is the core maintaining mechanism targeted in CBT-E relapse prevention.

Differential & comorbidity

• Differentiate binge-eating disorder without compensation, anorexia nervosa binge-purge subtype at low weight, and rumination or GI causes of vomiting.
• Consider Kleine-Levin syndrome, Prader-Willi syndrome and hypothalamic lesions when hyperphagia is atypical, and insulin omission in type 1 diabetes.
• Lifetime comorbidity is high: mood disorders near 70%, anxiety disorders about 65%, substance use near 35%, and borderline personality disorder near 30%.
• Suicide attempts occur in 25-35% and non-suicidal self-injury is common, with a standardized mortality ratio roughly twice the general population.
• Baseline workup includes potassium, magnesium, bicarbonate, amylase and ECG, plus dental referral and pregnancy screening as clinically indicated.

Pharmacologic treatment

• Fluoxetine 60 mg/day is the only FDA-approved agent and reduces binge and purge frequency by roughly 50-70% at doses above the antidepressant range.
• Other SSRIs such as sertraline 100-200 mg/day are second-line; combine with psychotherapy since medication alone rarely produces sustained abstinence.
• Bupropion is contraindicated in patients who purge because seizure risk rises sharply in the setting of electrolyte disturbance and low weight.
• Topiramate 100-250 mg/day lowers binge frequency but brings cognitive slowing, paresthesia, teratogenicity and weight loss that may be unwelcome.
• Replete potassium orally, avoid unnecessary QTc-prolonging drugs, and taper laxatives gradually with fiber and hydration to prevent rebound constipation.

Psychotherapy

• CBT-E is first-line at 20 sessions over 20 weeks, producing remission in roughly 30-50% and the largest effect size of any bulimia treatment.
• Guided self-help based on CBT is the NICE-recommended entry point for adults and an efficient first step within a stepped-care pathway.
• IPT matches CBT outcomes at long-term follow-up but works more slowly, making it a reasonable second-line choice after CBT non-response.
• DBT targets binge-purge behavior when emotion dysregulation, self-harm or borderline personality traits dominate the clinical picture.
• Regular eating every 3-4 hours, real-time self-monitoring records and stimulus control are the earliest behavioral changes and predict outcome.

Adjunct options

• Most patients are managed as outpatients; admit for potassium below 3.0, arrhythmia, hematemesis, acute suicidality or failed outpatient treatment.
• Nutritional counseling normalizes meal structure and corrects the belief that vomiting removes most calories, which it demonstrably does not.
• Dental evaluation, rinsing with water or bicarbonate rather than brushing after purging, and fluoride treatment protect remaining enamel.
• Measure change with the EDE-Q, weekly binge and purge logs, and the SCOFF questionnaire for screening in primary care settings.
• Family involvement and family-based treatment for bulimia benefit adolescents, and group formats reduce shame-driven secrecy in adults.

Clinical pearls

• Fluoxetine works for bulimia only at 60 mg/day; lower doses are effectively subtherapeutic.
• Normal weight does not mean medically stable: check potassium and an ECG at intake.
• Never prescribe bupropion to a purging patient, as the seizure risk is unacceptable.