What is anorexia nervosa?

Anorexia nervosa is most common among adolescent girls and young adult women. Characteristics of this disorder are an intense fear of weight gain and a disturbed body image, which motivates dietary restrictions and other weight loss behaviors, like purging or excessive physical activity. Serious medical morbidity and psychiatric comorbidity are the norm. The diagnostic criteria according to the DSM-IV versus the DSM-V are:

• A. DSM-IV: refusal to maintain a healthy weight.   
• A. DSM-V: restriction of energy intake relative to requirements, which leads to a significantly low BMI.   
• B. DSM-IV: intense fear of gaining weight, even though underweight.   
• B. DSM-V: intense fear of gaining weight, or persistent behavior that interferes with weight gain, even though at a significant low weight.   
• C. DSM-IV: disturbed body or weight image.  
• C. DSM-V: disturbed body image, undue influence of body shape and weight on self-evaluation, or persistent lack of recognition of low weight.  
• D. Amenorrhoea (absence of at least three or more consecutive menstrual cycles). 
• D. Amenorrhoea is no longer a criterion, based on conflicts with the inclusion of male individuals. This is also based on evidence showing no meaningful clinical difference between women with anorexia who menstruate and those who do not.

The DSM-V also classifies an atypical anorexia nervosa, which includes restrictive behaviors without meeting the low weight criterion. Severity in DSM-V is classified as extreme (BMI <15), severe (BMI <16), moderate (BMI <17) and mild (BMI> 17).

Diagnostic criteria according to the ICD-10 versus the ICD-11 are:

• A. ICD-10: weight loss, or in children a lack of weight gain, with a BMI at least 15% below normal.   
• A. ICD-11: significantly low BMI that is not caused by a health condition or lack of food.   
• B. ICD-10: weight loss that is self-induced.   
• B. ICD-11: low BMI associated with a persistent pattern of behaviors aimed at preventing weight gain.   
• C. ICD-10: a self-perception of being too fat.  
• C. ICD-11: low bodyweight is central to the person's self-evaluation or a disturbed body image.
• D. ICD-10: endocrine disorder.  
• D. ICD-11: none.  
• E. ICD-10: does not meet criteria A and B of bulimia nervosa.   
• E. ICD-11: none.   

What is the prevalence of anorexia nervosa?

The lifelong prevalence in women is around 1% and less than 0.5% in men. This can be as high as 5% if a broader criterion is used. 8 times more women than men suffer from anorexia nervosa. This ratio is smaller in children.

What are common comorbidities?

75% of patients with anorexia nervosa have a mood disorder, most commonly major depressive disorder, or have a lifelong history of at least one anxiety disorder. About 20% of patients have obsessive compulsive disorder. Prevalence of alcohol abuse/dependence is about 15%. This is less in the restrictive subtype. There is a non-specific relationship between anorexia nervosa and autism spectrum disorders. There are positive genetic correlations between anorexia nervosa and schizophrenia and between anorexia nervosa and obsessive compulsive disorder. Patients with anorexia nervosa display a broad variety of somatic complications. Up to 21% have osteoporosis and up to 54% have osteopenia of the lumbar spine. Patients have an increased life-time prevalence of auto-immune diseases, most prominently type 1 diabetes.

What is the prognosis?

As for prognosis, 59.6% show weight normalisation, 57.0% menstrual status normalisation and 46.8% normalisation of eating behavior. Patients with an onset below 17, have a better outcome than those with an adult onset, however prepubertal onset confers a worse outcome. About 5 in 1000 patients die due to medical complications, mostly because of starvation. The main issues leading to death are cardiac complications and serious infections. The purging subtype has the greatest mortality risk in male individuals. 

What causes anorexia nervosa?

Heritability of anorexia nervosa is estimated to range from 28% to 74%. A new genetic association between anorexia nervosa and schizophrenia has been found. People with anorexia nervosa show shifting difficulties and poor central coherence. They also have difficulties in socio-emotional processing, show attentional biases, impaired emotion recognition, regulation, and expressivity, and poor theory of mind. They may also have general reductions in gray and white matter, reduced grey matter in the left hypothalamus, in the basal ganglia and in the somatosensory cortex. This might recover after weight regain. Restricted eating can be a means to reduce negative affect caused by an imbalance between serotoninergic and dopaminergic systems. Developmental factors are hormonal changes and dysregulations in puberty. Anorexia nervosa is more common in low- and middle-income countries. This might be related to adopting western nutritional habits and thin ideal internalisation, which increases the number of people taking part in strict dieting/exercise. This in turn can trigger eating disorders.

How does diagnosis and treatment take place?

Assessment is done with an in-depth interview, a physical examination and other investigations. Access to help is associated with a better outcome. Treatment is most effective if the patient suffers from anorexia nervosa for less than three years. Most patients can be treated as outpatients if the disease is not too severe.

BulletPoint Summary

• Anorexia nervosa is most common among adolescent girls and young adult women. The lifelong prevalence in women is around 1% and less than 0.5% in men.

• Characteristics of this disorder are an intense fear of weight gain and a disturbed body image, which motivates dietary restrictions and other weight loss behaviors, like purging or excessive physical activity. 

• Comorbidity with other mental health disorders is common, with the most prevalent being mood disorders (75%). A lifelong history of at least one anxiety disorder is also common. Patients with anorexia nervosa display a broad variety of somatic complications, including osteoporosis and osteopenia of the lumbar spine.

• As for prognosis, 59.6% show weight normalization, 57.0% menstrual status normalization and 46.8% normalization of eating behavior. Patients with an onset below 17, have a better outcome than those with an adult onset, however prepubertal onset confers a worse outcome. About 5 in 1000 patients die due to medical complications.

• Heritability of anorexia nervosa is estimated to range from 28% to 74%.

• People with anorexia nervosa show difficulties with attention, socio-emotional processing and emotion regulation. There are reductions in gray and white matter of the brain. It is suggested that restricted eating can be a means to reduce negative emotions caused by imbalances between serotoninergic and dopaminergic systems.

• Treatment is most effective if the patient suffers from anorexia nervosa for less than three years.