Key Points
- Anorexia nervosa (AN) is a serious, potentially life-threatening psychiatric disorder characterised by: self-induced weight loss, a relentless pursuit of thinness, a morbid fear of weight gain and obesity, a distorted body image, and restriction of intake relative to requirements
- It has the highest mortality of any psychiatric condition, with death resulting from medical complications or suicide
- Diagnosis is clinical
- Treatment often involves a combination of medical stabilisation, nutritional rehabilitation, and psychological and behavioural therapies. Involvement of the family is crucial to the care of younger patients
- Olanzapine may help with weight gain.
1. Definition
Anorexia nervosa is an eating disorder characterised by:
- Significantly low body weight for the individual’s age and height
- Intense fear of gaining weight or becoming fat, despite being underweight
- Distorted body image or an undue emphasis on body weight or shape in self-evaluation.
It can be further classified into two subtypes:
- Restricting type: Weight loss is primarily achieved through dieting, fasting, or excessive exercise.
- Binge-eating/purging type: Individuals engage in binge eating or purging behaviors (e.g., self-induced vomiting, misuse of laxatives).
2. Epidemiology
- Prevalence: Anorexia nervosa affects approximately 0.3-0.6% of women and 0.1-0.3% of men. It is more common in adolescent girls and young women, with the average age of onset being in the mid-teens
- Gender differences: While anorexia predominantly affects females, the number of cases in males is rising
- Mortality: The mortality rate is around 5-10% due to medical complications and suicide.
3. Risk factors
- Biological factors: Family history of eating disorders, mood disorders, or substance abuse increases susceptibility
- Psychological factors: Perfectionism, obsessive-compulsive traits, low self-esteem, and anxiety disorders are common predisposing factors
- Sociocultural factors: Cultural pressure to be thin, particularly in Western societies, increases the risk. Occupations or hobbies that emphasise body appearance, such as modeling, dancing, or athletics, are also associated
- Genetic predisposition: Twin and family studies suggest a genetic component, with heritability estimated at 50-60%
3. Causes
The exact cause of anorexia nervosa is unknown. It appears to be multifactorial and involves an interaction of genetic, biological, environmental, and psychological factors:
- Genetic predisposition: Variants in certain genes involved in appetite regulation and mood may contribute
- Neurobiological factors: Abnormalities in neurotransmitters like serotonin, dopamine, and norepinephrine may affect appetite, mood, and anxiety
- Psychological factors: Individuals with anorexia often have perfectionistic tendencies and experience heightened anxiety, which drives obsessive behaviors around food and weight control
- Environmental influences: Media, societal ideals of thinness, and stress from family dynamics or trauma can trigger or exacerbate the condition.
4. Symptoms
Physical symptoms
- Extreme weight loss or failure to make expected weight gains during adolescence
- Amenorrhoea in women or delayed puberty in adolescents
- Bradycardia, hypotension, and hypothermia
- Lanugo (fine hair growth) as the body tries to conserve heat
- Dry skin and brittle nails
- Peripheral oedema, especially in refeeding phases.
Behavioural and psychological symptoms
- Preoccupation with food, dieting, or weight despite being underweight
- Intense fear of gaining weight
- Ritualistic eating habits, such as cutting food into small pieces, avoiding meals, or hiding food
- Denial of the severity of their low body weight or behaviours
- Excessive exercise or compulsive physical activity.
5. Diagnosis
The diagnosis of anorexia nervosa is based on clinical evaluation and criteria set out by the DSM-5. Key diagnostic features include:
- Restriction of energy intake leading to significantly low body weight
- Intense fear of gaining weight or becoming fat, even though underweight
- Distorted body image, undue influence of body weight/shape on self-worth, or lack of recognition of the seriousness of low body weight.
Investigation
Initial investigations are essential to assess the severity of malnutrition and identify potential complications:
- Blood tests:
- Full blood count (FBC): May reveal anaemia, leucopenia, or thrombocytopenia.
- Electrolytes: Hypokalaemia, hyponatraemia, and metabolic alkalosis are common in purging behaviour
- Liver function tests (LFTs): Elevated liver enzymes may indicate malnutrition
- Thyroid function tests: Can show ‘sick euthyroid syndrome’
- Bone profile: Hypocalcaemia and hypophosphataemia can occur, especially during refeeding.
- Electrocardiogram (ECG)
- Assess for bradycardia, QT prolongation, and other arrhythmias, which are common due to malnutrition and electrolyte disturbances.
- Bone densitometry
- Consider in cases of chronic anorexia to assess for osteopenia or osteoporosis.
Differential diagnosis
Several conditions can mimic anorexia nervosa and should be excluded:
- Hyperthyroidism: Can present with weight loss, anxiety, and tachycardia
- Inflammatory bowel disease (IBD): Causes weight loss and gastrointestinal symptoms
- Malignancy: Unexplained weight loss should prompt evaluation for an underlying malignancy
- Depression: Can present with weight loss and loss of appetite but lacks the body image distortion seen in anorexia
- Diabetes mellitus (Type 1): Can cause weight loss and may be mistaken for anorexia in its early stages.
7. Treatment
Management of anorexia nervosa requires a multidisciplinary approach, involving medical stabilization, nutritional rehabilitation, and psychological support:
- Medical stabilisation
- Hospitalisation may be required for patients with severe malnutrition, dehydration, electrolyte imbalances, or cardiac instability
- Refeeding syndrome should be monitored, with gradual reintroduction of calories and electrolyte supplementation (particularly phosphate).
- Nutritional rehabilitation
- A key goal is weight restoration to a healthy range. This involves a structured meal plan with gradual caloric increases
- Dietitians play a critical role in meal planning and monitoring caloric intake.
- Psychological therapies
- Cognitive-behavioral therapy (CBT) tailored to eating disorders is the most evidence-based treatment for anorexia nervosa
- Family-based therapy (FBT) is particularly effective in adolescents and involves the family in supporting the patient’s recovery
- Motivational interviewing may be helpful in engaging patients who are resistant to treatment.
- Pharmacotherapy
- There is no specific medication for anorexia nervosa, but antidepressants (such as SSRIs) may be used to treat comorbid depression or anxiety
- Olanzapine, an atypical antipsychotic, may help in some cases to reduce preoccupation with weight and food.
8. Complications
Anorexia nervosa can lead to severe medical and psychological complications, many of which are life-threatening:
- Cardiovascular complications: Bradycardia, arrhythmias, and heart failure
- Endocrine abnormalities: Amenorrhoea, infertility, and osteopenia/osteoporosis
- Gastrointestinal issues: Gastroparesis, constipation, and malabsorption
- Electrolyte imbalances: Hypokalaemia and hyponatraemia, especially in those who engage in purging behaviours
- Refeeding syndrome: A potentially fatal complication during nutritional rehabilitation
- Psychiatric comorbidities: Depression, anxiety, obsessive-compulsive disorder (OCD), and a high risk of suicide.
9. Prognosis
The prognosis for anorexia nervosa varies:
- Recovery rates range from 50-70%, but many patients experience chronic illness or relapse.
- Mortality: Approximately 5-10% of individuals with anorexia nervosa die due to medical complications or suicide.
- Early intervention, particularly in adolescence, improves outcomes and reduces the risk of long-term complications.
10. Prevention
Preventing anorexia nervosa is challenging due to its multifactorial nature, but efforts can be made in several areas:
- Public health initiatives promoting healthy body image and reducing societal pressures around thinness
- Education and awareness programs, particularly in schools and among adolescents, to identify at-risk individuals early
- Early detection by healthcare professionals is crucial, as early intervention is associated with better outcomes.
Conclusion
Anorexia nervosa is a complex and life-threatening disorder requiring a careful, multidisciplinary approach. Early diagnosis, psychological support, nutritional rehabilitation, and medical management are key to improving the long-term outcomes for patients with this condition.
