Anorexia Nervosa
Restriction of intake leading to significantly low body weight, intense fear of weight gain, and disturbed body image.
Also known as: anorexia, anorexia nervosa, restrictive eating disorder
Overview
An eating disorder characterized by restriction of energy intake leading to significantly low body weight relative to age, sex, developmental trajectory, and physical health; intense fear of gaining weight or persistent behavior interfering with weight gain; and disturbance in the way one's body weight or shape is experienced.
Epidemiology
Lifetime prevalence ~1% in women, ~0.3% in men. Peak onset adolescence/young adulthood. Highest mortality of any psychiatric disorder (~5-6x age-matched controls).
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Risk factors
- Female sex, adolescence
- Family history of eating, mood, or anxiety disorders
- Perfectionistic, anxious, or obsessional temperament
- Cultural and athletic pressures emphasizing thinness (dance, gymnastics, wrestling, running)
- Early menarche
- Type 1 diabetes ('diabulimia')
Pathophysiology
Polygenic vulnerability with disturbed reward processing, altered serotonergic signaling, and structural/functional changes in insular and frontal cortices. Starvation itself perpetuates rigid cognition and physiologic adaptations.
Clinical presentation
Symptoms
- Severe dietary restriction; rule-driven eating; excessive exercise; calorie counting; body checking
- Subtypes: restricting type vs binge-eating/purging type
- Amenorrhea common but not required for DSM-5-TR diagnosis
- Cold intolerance, fatigue, constipation, dizziness, syncope
Signs / physical exam
- Cachexia, lanugo, dry skin, brittle hair, peripheral edema
- Bradycardia, hypotension, hypothermia, orthostasis
- Russell's sign (knuckle calluses) if purging
- Parotid hypertrophy with vomiting
- Dental erosion of lingual enamel from vomiting
Differential diagnosis
- Bulimia nervosa — Binge-purge cycles with normal or above-normal weight
- Avoidant/restrictive food intake disorder (ARFID) — Low intake without body image disturbance — sensory aversion, fear of aversive consequences, lack of interest
- Body dysmorphic disorder — Preoccupation with appearance flaw not centered on weight
- Medical causes of weight loss — Hyperthyroidism, IBD, malignancy, T1DM, celiac, Addison — workup if behavioral history atypical
- MDD with poor appetite — Weight loss secondary to anhedonia; body image not distorted
Diagnostic workup
Diagnostic criteria
DSM-5-TR: (A) Restriction of energy intake relative to requirements leading to significantly low body weight in context of age/sex/developmental trajectory/health; (B) Intense fear of gaining weight or becoming fat, or persistent behavior interfering with weight gain; (C) Disturbance in body weight/shape experience, undue influence on self-evaluation, or lack of recognition of seriousness of low weight. Severity by BMI: mild >=17, moderate 16-16.99, severe 15-15.99, extreme <15. Subtype: restricting vs binge-eating/purging.
Labs
- CBC (leukopenia), CMP (hypokalemia, hypomagnesemia, hypophosphatemia, hyponatremia, low BUN, transaminitis), Mg, phosphate
- TSH (often low T3), LH/FSH/estradiol (hypothalamic suppression), morning cortisol
- ECG (bradycardia, QT prolongation)
- DEXA after 6-12 months of amenorrhea (osteopenia/osteoporosis)
- B12, vitamin D, iron studies
Imaging
- DEXA for bone density
- ECG essential prior to refeeding
Diagnostic algorithm
| DSM-5-TR severity | BMI (adults) |
|---|---|
| Mild | >=17 |
| Moderate | 16-16.99 |
| Severe | 15-15.99 |
| Extreme | <15 |
Treatment
First-line
- Multidisciplinary team — primary care, mental health, dietitian, family
- Family-based treatment (Maudsley) — first-line for adolescents
- Cognitive behavioral therapy for eating disorders (CBT-ED), enhanced CBT (CBT-E) — adults
- Nutritional rehabilitation with structured meal plan and gradual weight restoration
- Medical hospitalization for severe malnutrition, hemodynamic instability, electrolyte derangement, suicidality
Second-line / adjunct
- Olanzapine — modest evidence for weight restoration and obsessional thinking in adults
- SSRIs only for treating comorbid depression/anxiety — NOT effective for core anorexia symptoms in low-weight state
- Residential or partial hospitalization programs
- Bisphosphonates considered for low bone density only in select cases
Complications
- Refeeding syndrome — hypophosphatemia, hypokalemia, hypomagnesemia, thiamine deficiency, fluid shifts; cardiac failure and arrhythmia; start at conservative caloric load (e.g., 1200-1500 kcal/day) and increase gradually, replete electrolytes proactively
- Cardiac: bradycardia, prolonged QT, pericardial effusion, cardiomyopathy, sudden cardiac death
- Endocrine: amenorrhea, hypothalamic hypogonadism, infertility, low bone density
- GI: gastroparesis, constipation, SMA syndrome
- Renal calculi, electrolyte disturbances
- Suicide (~20% of mortality)
PANCE pearls
- Hospitalization criteria (one or more): HR <40, SBP <90 (or marked orthostasis), temp <36C, K <3, hypoglycemia, severe dehydration, BMI <15, acute medical instability, suicidality, refractory outpatient progress.
- Refeeding syndrome occurs in first 1-2 weeks — check phosphate, magnesium, potassium daily; supplement thiamine BEFORE refeeding.
- Bone density loss is largely irreversible — weight restoration is the most important intervention; estrogen replacement does NOT prevent bone loss in this population.
- Family-based treatment outperforms individual therapy in adolescents — engage parents as agents of refeeding.
References
- APA 2023 — American Psychiatric Association Practice Guideline for the Treatment of Patients with Eating Disorders, 4th ed. (2023)
- NICE NG69 — NICE Guideline 69: Eating disorders: recognition and treatment
- AED Medical Care Standards — Academy for Eating Disorders. Medical Care Standards, 4th ed.
- DSM-5-TR — American Psychiatric Association. DSM-5-TR (2022)
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