University of Gothenburg
boy refusing food

Definition and classification

Anorexia nervosa (AN) is a severe eating disorder that primarily affects adolescent girls. Restrictive eating (often combined with increased physical activity) results in extreme weight loss driven by a fear of weight gain, distorted self-image and fear of calories and fat. Absence of menstrual periods (among girls who have previously had them) is often an early symptom, but is no longer a required symptom for diagnosis. ICD-11 (WHO 2018) lists alternative weight criteria: rapid weight loss over the last 6 months or stalled weight gain relative to the individual’s weight curve. Rapid weight loss can be a distinguishing trait for children with AN.

The clinical eating disorders anorexia nervosa, bulimia nervosa, binge-eating disorder and “other specified eating disorders” such as ARFID (Avoidant/restrictive food intake disorder) are described in DSM-5, APA 2013. The focus here is on restrictive eating that leads to malnutrition and underweight.


Maria Råstam Bergström


One-year prevalence could be as high as 1 per cent among teenage girls. Age of onset is typically 12 to 15 years. A large nationally representative study of ages 8-17 (clinically reported cases in the UK and Ireland) recently estimated AN incidence at 13.7 per 100,000 person years (25.6 girls; 2.3 boys). A large Finnish population study examining the risk ages 10-24 showed an incidence of 15.7 per 100,000 person years.


AN develops when an individual with a genetic predisposition for eating disorder behaviours is affected by environmental factors like family, attachment and sociocultural factors. Dieting can trigger eating disorder symptoms. Studies suggest that both girls and boys are influenced by their environment when it comes to self-image, especially if they are bullied. Intuitive eating seems to have an inverse correlation to BMI for both sexes, and also lower the risk of eating disorder behaviours. A sustaining factor in AN is that restrictive eating reduces dysphoria while overeating alleviates negative emotions.

Twin-based heredity is estimated at 50-60 per cent. What exactly is inherited has as of yet not been determined, but a large genetic study indicates that AN could be both a metabolic and a psychiatric disorder. However, a prospective Swedish AN study over three decades found that perfectionist traits were predictive of better prognosis.

Mental symptoms

Dieting, particularly intense dieting, may trigger weight loss, phobic control of food intake, intense exercise and social isolation. Initial stages are marked by severe hunger and unstable weight. The hunger causes at least half of all cases to binge-eat and vomit. Fatigue, anxiety, dejection, dizziness and a restless need for movement eventually follow as well. Obsessive-compulsive behaviour and a need for control are very prominent.

Somatic symptoms

Underweight or stalled growth (in children), weight fluctuations and malnutrition lead to electrolyte disorders, metabolic and endocrine changes. Somatic changes are secondary to starvation and long-term underweight and usually reversible once weight is restored to normal. Secondary amenorrhea is common and menstruation is often delayed in cases of prepubescent onset. Slow heartbeat, low blood pressure, hypothermia and dehydration are common. Skin, hair and tooth quality are all affected. Gastrointestinal issues are virtually always present and may subside once weight is restored to normal, but is overrepresented in follow-ups of AN cases treated at CAP.

Those who were overweight before their weight loss might have muscle weakness even when they have a surplus of body fat and normal BMI. Insufficient energy intake leads to a low level of anabolic hormones. A large part of initial weight gain is peripheral body fat and muscle mass only starts to normalise once the endocrine system has stabilised. Malnutrition and starvation-induced sex hormone deficit can lead to abnormal development of the brain. Deteriorated brain function is restored in most but not all cases upon recovery (in some cases it can be a primary deviance).

Severe starvation over several years can lead to heart failure, kidney failure and osteoporosis with fractures. Symptomatic vitamin deficiency occurs in cases of extreme long-term undernutrition. Excess mortality with regard to age is 6-10 percent and related to the eating disorder (infections, electrolyte balance disorder, complications of extreme undernutrition) but also suicide.

Differential diagnoses like hyper- and hypothyroidism, diabetes, gastrointestinal disease or tumour disease are usually not hard to differentiate from AN but may as concurrent diagnoses exacerbate the eating disorder or contribute to triggering eating disorder behaviour.

Concurrent psychiatric diagnoses and differential diagnoses

  • Depression and anxiety are almost always present throughout the duration of the eating disorder. In rare cases, the eating disorder is part of an affective disorder, thus extending the duration of the condition and increasing the risk of relapsing later in life. Obsessive-compulsive disorder (OCD) is overrepresented in AN and precedes AN by several years in one third of all cases. Obsessive-compulsive symptoms like extreme cleanliness, orderliness and demand for symmetry are especially common in cases where both OCD and AN are present.


  • Delirium and psychotic symptoms occur in cases of severe starvation. More than 10 per cent of AN patients hear condescending, menacing voices warning them about food and weight gain. If there are no other signs of psychosis, these could be personal thoughts amplified to a psychotic degree, and this is important to know before treatment.


  • Neurodevelopmental disorders like autism and ADHD are overrepresented in AN and diagnosed based on accounts from family members centred on social interaction/communication and activity/attention in childhood. If such issues had not been established previously, one should not make additional diagnoses of autism and ADHD until stable improvement of AN has been achieved.


  • Atypical AN can develop into the full syndrome. Even when this is not the case, the medical and psychological consequences are often comparable to AN and it does not seem easier to recover from. Over a third of AN cases develop bulimic behaviour to the extent that they meet criteria for bulimia nervosa. Psychogenic vomiting and dysphagia can in rare cases be mistaken for AN.


  • ARFID is a diagnosis meant for individuals with low nutritional intake causing any of the following: significant weight loss and/or significant malnutrition and/or dependency on enteral nutrition and/or a noticeable deterioration in psychosocial function, but no desire to be thin. Onset is earlier than that of AN and boys and girls are equally affected. Autism is diagnosed in up to 20 per cent of all cases. Causes include abnormal taste perception and/or appetite and/or fear-based aversion to consuming and swallowing food. A small number of epidemiological studies point to a likely prevalence among children and adolescents of 3 to 5 per cent. Some cases feature selective eating where the number of acceptable dishes is heavily limited for long periods of time. The ARFID diagnosis allows us to avoid medicalising selective eating among the 20 per cent of all small children where this is just a passing phase. A few with ARFID eventually develop AN. Children and adolescents with ARFID run the same risk of poor mental health as those with AN.

Treatment of AN

The starvation affects vital bodily functions, so putting a stop to it is the first priority of treatment. The best possible treatment requires an interdisciplinary team that is knowledgeable about AN and other eating disorders, developmental problems and nutrition in growing individuals. Family therapy is recommended for adolescent AN patients. Individual therapy is recommended for patients over 18 years of age. Cognitive behavioural therapy is effective in treating AN. If neuropsychiatric problems have been present since birth, psychoeducational efforts (accounting for cognitive ability) must be implemented. No medication can specifically treat the entire symptomatology of AN. Sometimes medical treatment of severe depression and/or anxiety must be considered.

Outcome of AN

On average, AN lasts for three years. Many have a strained relationship with food and weight for several years, if not their entire lives. Prospective follow-up for 30 years of teenage onset AN showed lingering eating disorder in 20 per cent of all cases. Obsessive compulsions and social negativism as dominant personality traits contributed to deteriorated function with social isolation and decreased working capacity. An important aspect is that 20 per cent never seek treatment. In line with other studies of typical teenage anorexia, the majority, including among those who had not been treated, had a good prognosis and no increase in mortality. Patients with drawn out recurring AN have a more unfavourable prognosis. A Swedish study showed an almost tenfold increase in risk-adjusted mortality among AN inpatients, either caused by starvation or suicide, or related to alcohol, epilepsy or diabetes.