Anorexia Nervosa
Summary
Anorexia nervosa (AN) is a serious psychiatric disorder characterised by restriction of energy intake leading to significantly low body weight, intense fear of gaining weight, and disturbance in self-perception of weight or shape. It has the highest mortality rate of any psychiatric disorder, with death from medical complications or suicide. AN predominantly affects adolescent females but occurs in all age groups and genders. Treatment requires a multidisciplinary approach including nutritional rehabilitation, psychological therapy (Family-Based Treatment for adolescents, CBT-ED for adults), and medical stabilisation. Refeeding syndrome is a life-threatening complication requiring careful monitoring.
Key Facts
- Prevalence: 0.3-1% of young women; 0.1-0.3% of young men
- Peak onset: 15-19 years
- Mortality: Highest of any psychiatric disorder (5-20% lifetime mortality)
- Cause of death: 50% medical complications, 50% suicide
- Key treatment: Family-Based Treatment (adolescents), CBT-ED/MANTRA (adults)
- Critical risk: Refeeding syndrome (monitor phosphate, K+, Mg2+)
Clinical Pearls
Refeeding Syndrome: Starting nutrition too rapidly in severely malnourished patients causes hypophosphataemia, hypokalaemia, and hypomagnesaemia — leading to cardiac arrhythmias, heart failure, and death. Start low, go slow.
The Vital Signs: Bradycardia (HR less than 50), hypotension (systolic less than 90), and hypothermia (temp less than 35°C) indicate extreme medical risk and require inpatient admission.
The MARSIPAN Guidelines: UK guidelines for managing Really Sick Patients with Anorexia Nervosa — essential risk assessment framework.
Why This Matters Clinically
Anorexia nervosa is a life-threatening condition that often presents to non-psychiatric services. Early recognition, medical stabilisation, and referral to specialist eating disorder services save lives. Refeeding syndrome is preventable with careful nutritional management.
Incidence & Prevalence
- Prevalence (females): 0.3-1%
- Prevalence (males): 0.1-0.3% (likely underdiagnosed)
- Incidence: 8-13 per 100,000 per year
- Age of onset: Peak 15-19 years
- Trend: Increasing incidence, particularly in younger ages
Demographics
| Factor | Details |
|---|---|
| Age | Peak onset 15-19 years; can occur at any age |
| Sex | Female:Male ratio 10:1 in clinical populations |
| Ethnicity | All ethnic groups (historically underdiagnosed in non-white populations) |
| Socioeconomic | No clear association; affects all groups |
Risk Factors
Non-Modifiable:
- Female sex
- Family history of eating disorders
- Personal history of dieting
- Perfectionist or anxious personality traits
- Autism spectrum traits
Modifiable:
| Factor | Impact |
|---|---|
| Weight-related teasing/bullying | Increases risk |
| Participation in aesthetic sports (gymnastics, ballet) | Increased prevalence |
| Social media exposure to thin ideals | Increasing evidence |
| Early dieting | Strong association |
Mechanism
Step 1: Genetic and Psychological Predisposition
- Heritability 50-80%
- Perfectionism, anxiety, low self-esteem, obsessionality
- Neurobiological differences in reward processing and body perception
Step 2: Dietary Restriction and Weight Loss
- Energy intake restriction leads to weight loss
- Positive reinforcement from weight loss (self-esteem, control)
- Physiological changes reinforce restriction (starvation reduces appetite)
Step 3: Starvation Physiology
- Reduced metabolic rate (adaptive thermogenesis)
- Hormonal changes: Low leptin, low sex hormones, high cortisol
- Cardiac: Bradycardia, hypotension, reduced cardiac muscle mass
- Bone: Osteopenia/osteoporosis
- Haematological: Pancytopenia
- GI: Delayed gastric emptying, constipation
Step 4: Psychological Entrenchment
- Distorted body image persists despite emaciation
- Egosyntonic symptoms (patient does not perceive illness)
- Fear of weight gain intensifies with treatment
Classification
DSM-5 Subtypes:
| Subtype | Definition |
|---|---|
| Restricting Type | Weight loss through dieting, fasting, exercise; no regular binging/purging |
| Binge-Purge Type | Episodes of binge eating and/or purging (vomiting, laxatives, diuretics) |
Severity (DSM-5):
| Severity | BMI | Notes |
|---|---|---|
| Mild | ≥17 kg/m² | |
| Moderate | 16-16.99 kg/m² | |
| Severe | 15-15.99 kg/m² | |
| Extreme | less than 15 kg/m² | High medical risk |
Symptoms
Core Features:
Behaviours:
Physical Symptoms:
Signs
Red Flags
[!CAUTION] Medical Emergency — Urgent admission if:
- HR less than 40 bpm (awake) or less than 30 (sleep)
- Systolic BP less than 90 mmHg or postural drop greater than 20 mmHg
- Temperature less than 35°C
- BMI less than 13 kg/m² or rapid weight loss (greater than 1kg/week)
- Syncope or near-syncope
- Hypoglycaemia (BM less than 3 mmol/L)
- Significant electrolyte disturbance (especially hypokalaemia)
- Suicidal ideation or active self-harm
Structured Approach
General:
- Weight, height, BMI
- Vital signs: HR, BP (lying and standing), temperature
- Signs of dehydration
Cardiovascular:
- Bradycardia, low BP
- Postural hypotension
- Peripheral oedema
Skin:
- Lanugo hair (trunk, face)
- Dry skin, poor turgor
- Hypercarotenaemia (orange palms/soles)
Musculoskeletal:
- Muscle wasting, weakness
- SQUAT test (ability to rise from squat)
Oral:
- Dental erosion, parotid enlargement (purging)
- Russell's sign (calluses on knuckles from induced vomiting)
Special Tests
| Test | Technique | Positive Finding | Purpose |
|---|---|---|---|
| SUSS Test | Sit-up, squat, stand | Unable to complete = severe muscle weakness | Assess medical risk |
| Postural BP | Lying → standing BP | Drop greater than 20 mmHg systolic | Assess dehydration/autonomic dysfunction |
| Temperature | Core temperature | Less than 35.5°C concerning | Assess severity |
First-Line
- Weight and height — Calculate BMI
- Vital signs — HR, BP (lying/standing), temperature
- ECG — Bradycardia, prolonged QTc, arrhythmias
- Baseline bloods — FBC, U&E, LFTs, TFTs, glucose
Laboratory Tests
| Test | Expected Finding | Purpose |
|---|---|---|
| FBC | Leukopenia, anaemia, thrombocytopenia (pancytopenia) | Bone marrow suppression |
| U&Es | Hypokalaemia (purging), low sodium | Electrolyte monitoring |
| Phosphate, Magnesium | May be low; critical for refeeding | Refeeding syndrome risk |
| Glucose | Hypoglycaemia | Starvation |
| LFTs | Elevated transaminases | Hepatic steatosis |
| TFTs | Low T3, normal TSH (euthyroid sick syndrome) | Baseline |
| Albumin | May be low (late marker) | Nutritional status |
Imaging
| Modality | Findings | Indication |
|---|---|---|
| ECG | Bradycardia, QTc prolongation, arrhythmias | All patients |
| DEXA scan | Low bone mineral density | If AN greater than 6-12 months |
| Echocardiogram | Pericardial effusion, reduced LV mass | If significant cardiac symptoms |
Management Algorithm
ANOREXIA NERVOSA
↓
┌─────────────────────────────────────────┐
│ MEDICAL RISK ASSESSMENT │
│ (MARSIPAN/Junior MARSIPAN) │
│ Weight, BMI, HR, BP, ECG, bloods │
└─────────────────────────────────────────┘
↓
┌─────────────────────────────────────────┐
│ RISK STRATIFICATION │
├─────────────────────────────────────────┤
│ HIGH RISK → Medical admission │
│ (HR<40, BP<90, BMI<13, hypoglycaemia) │
│ │
│ MODERATE RISK → Day patient/intensive │
│ outpatient │
│ │
│ LOW RISK → Outpatient treatment │
└─────────────────────────────────────────┘
↓
┌─────────────────────────────────────────┐
│ TREATMENT COMPONENTS │
├─────────────────────────────────────────┤
│ 1. NUTRITIONAL REHABILITATION │
│ (Start low, go slow; monitor PO4) │
│ │
│ 2. PSYCHOLOGICAL THERAPY │
│ < 18: Family-Based Treatment (FBT) │
│ Adult: CBT-ED, MANTRA, or SSCM │
│ │
│ 3. MEDICAL MONITORING │
│ Weight, vitals, bloods │
│ │
│ 4. PSYCHIATRIC TREATMENT │
│ Treat comorbidities (depression, │
│ anxiety, OCD) │
└─────────────────────────────────────────┘
Emergency Medical Management
Refeeding Syndrome Prevention:
- Start feeding cautiously (10-20 kcal/kg/day in high risk)
- Supplement thiamine 200-300mg daily (before feeding)
- Supplement phosphate, potassium, magnesium prophylactically
- Monitor electrolytes daily initially
- Gradually increase calories (max 500 kcal increase every 2-3 days)
Indications for Inpatient Admission:
- BMI less than 13 kg/m²
- Rapid weight loss (greater than 1kg/week)
- HR less than 40 bpm
- Systolic BP less than 90 mmHg
- Hypoglycaemia
- Severe electrolyte disturbance
- Suicidal ideation
- Failed outpatient treatment
Psychological Treatment
Adolescents (under 18):
- Family-Based Treatment (FBT) — First-line; Maudsley method
- 15-20 sessions over 6-12 months
- Parents take control of refeeding initially
Adults:
- CBT-ED — Individual CBT adapted for eating disorders
- MANTRA — Maudsley Model of Anorexia Nervosa Treatment for Adults
- SSCM — Specialist Supportive Clinical Management
Medical Management
| Drug | Indication | Notes |
|---|---|---|
| Thiamine | All malnourished patients | Prevents Wernicke's during refeeding |
| Phosphate supplements | Refeeding syndrome | Polyfusor or Phosphate-Sandoz |
| Multivitamin | Nutritional deficiency | Routine |
| SSRIs (fluoxetine) | Comorbid depression (after weight restoration) | Not effective for core AN symptoms |
| Olanzapine | Severe anxiety, weight gain | Limited evidence; consider in resistant cases |
Mental Health Act
When to consider compulsory treatment:
- Patient refusing treatment despite life-threatening physical deterioration
- AN is treatable, and treatment can be provided against will
- Nasogastric feeding may be authorised under MHA if necessary to save life
Disposition
- Admit if: High medical risk, failed outpatient treatment, psychiatric emergency
- Discharge if: Medically stable, engaged with outpatient ED service
- Follow-up: Weekly weight monitoring initially; ED service lead care
Immediate (Acute)
| Complication | Incidence | Presentation | Management |
|---|---|---|---|
| Refeeding syndrome | 5-25% (high risk patients) | Hypophosphataemia, cardiac failure | Slow refeeding, electrolyte replacement |
| Cardiac arrhythmia | Variable | QTc prolongation, VT, asystole | ECG monitoring, correct electrolytes |
| Hypoglycaemia | Common | Confusion, seizure, collapse | IV glucose |
Early (Weeks-Months)
- Infection: Immunocompromise from malnutrition
- Gastroparesis: Delayed gastric emptying — early satiety, bloating
- Peripheral oedema: During refeeding (usually transient)
Late (Months-Years)
- Osteoporosis: Up to 50% have low bone density — fractures
- Infertility: Hypothalamic amenorrhoea
- Cardiac structural changes: Reduced left ventricular mass
- Death: 5-20% lifetime mortality (medical complications, suicide)
Natural History
- Without treatment: Chronic course with high mortality
- Average duration of illness: 6-7 years
- Mortality: 5-20% lifetime (highest of any psychiatric disorder)
Outcomes with Treatment
| Variable | Outcome |
|---|---|
| Full recovery | 40-50% |
| Partial recovery | 30% |
| Chronic course | 20% |
| Mortality | 5-20% lifetime |
Prognostic Factors
Good Prognosis:
- Younger age of onset
- Shorter duration before treatment
- No binge-purge behaviours
- Good family support
- Higher motivation to change
Poor Prognosis:
- Longer duration of illness
- Lower BMI at presentation
- Binge-purge subtype
- Comorbid depression or personality disorder
- Poor social support
- Previous treatment failure
Key Guidelines
- NICE NG69 (2017) — Eating disorders: recognition and treatment. NICE NG69
- MARSIPAN (2022) — Management of Really Sick Patients with Anorexia Nervosa (RCPsych, RCPCH).
- Junior MARSIPAN — For children and young people.
Landmark Trials
FBT Studies (Lock et al.) — Family-Based Treatment
- Multiple RCTs
- Key finding: FBT superior to individual therapy in adolescents
- Clinical Impact: FBT is first-line for adolescent AN
ANTOP Trial (2014) — Focal Psychodynamic Therapy vs CBT-E vs TAU
- 242 adult patients
- Key finding: All active treatments superior to TAU; no difference between FPT and CBT-E
- Clinical Impact: Supports CBT-ED for adult AN
Evidence Strength
| Intervention | Level | Key Evidence |
|---|---|---|
| Family-Based Treatment (adolescents) | 1b | Multiple RCTs |
| CBT-ED (adults) | 1b | ANTOP, other RCTs |
| MANTRA (adults) | 1b | RCT evidence |
| Refeeding protocols | 2a | Cohort studies, guidelines |
What is Anorexia Nervosa?
Anorexia nervosa is a serious mental health condition where a person restricts how much they eat, has an intense fear of gaining weight, and sees their body differently from how others see it. Even when very underweight, someone with anorexia may feel they are too heavy.
Why does it matter?
Anorexia is dangerous because severe starvation affects every organ in your body, especially your heart. It has the highest death rate of any mental illness. However, with the right treatment, most people can recover.
How is it treated?
- Medical stabilisation: If you are very unwell, you may need to be in hospital to correct nutritional deficiencies safely.
- Nutritional rehabilitation: Gradually increasing food intake with close monitoring to prevent refeeding syndrome.
- Therapy:
- For teenagers: Family-Based Treatment (FBT) — your family helps you to eat and recover
- For adults: CBT for eating disorders, or similar therapy
- Treating other conditions: Depression, anxiety, or OCD are often treated alongside.
What to expect
- Recovery takes time — often months to years
- Weight gain is necessary for physical and mental recovery
- Relapses can happen but do not mean failure
- Long-term support is usually needed
When to seek help
Seek help urgently if you or someone you know has:
- Very low weight with ongoing weight loss
- Fainting, dizziness, or chest pain
- Very slow heart rate
- Thoughts of suicide or self-harm
- Refusal to eat despite clear physical deterioration
Primary Guidelines
- National Institute for Health and Care Excellence. Eating disorders: recognition and treatment (NG69). 2017. NICE NG69
- Royal College of Psychiatrists. MARSIPAN: Management of Really Sick Patients with Anorexia Nervosa. 2022.
Key Studies
- Lock J, et al. Randomized clinical trial comparing family-based treatment with adolescent-focused individual therapy for adolescents with anorexia nervosa. Arch Gen Psychiatry. 2010;67(10):1025-32. PMID: 20921118
- Zipfel S, et al. Focal psychodynamic therapy, cognitive behaviour therapy, and optimised treatment as usual in outpatients with anorexia nervosa (ANTOP study): randomised controlled trial. Lancet. 2014;383(9912):127-37. PMID: 24131861
- Mehler PS, Brown C. Anorexia nervosa — medical complications. J Eat Disord. 2015;3:11. PMID: 25834735
Further Resources
- Beat Eating Disorders: beateatingdisorders.org.uk
- MAUDSLEY Centre for Eating Disorders: maudsleyparents.org
- NHS Eating Disorders: nhs.uk/mental-health/conditions/anorexia
Last Reviewed: 2025-12-24 | MedVellum Editorial Team
Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists.