All subjects · Psychology · WPS04 Clinical Psychology and Psychological Skills

Anorexia nervosa: symptoms and features

Edexcel IAL Psychology · WPS04 Clinical Psychology and Psychological Skills

If your centre chose anorexia nervosa for spec 8.1.5, you need its symptoms, features and DSM-5 and ICD-11 classification. Anorexia is a serious illness with real physical risks; recovery is possible with specialist help.

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DSM-5 criteria

A. Restriction of energy intake leading to significantly low body weight for age, sex, development and physical health.

B. Intense fear of gaining weight or becoming fat, or persistent behaviour that prevents weight gain.

C. Disturbance in how body weight or shape is experienced, self-worth unduly influenced by weight or shape, or persistent lack of recognition of how serious the low weight is.

Subtypes (last 3 months): restricting type and binge-eating/purging type.

Severity (adults, BMI kg/m²)	Range
Mild	17 or more
Moderate	16 to 16.99
Severe	15 to 15.99
Extreme	Under 15

ICD-11 (6B80)

Significantly low body weight: a commonly used cut-off is a BMI below 18.5 in adults (below the 5th BMI-for-age percentile in children); rapid weight loss (more than 20% of body weight in 6 months) can replace the low-weight criterion.
A persistent pattern of behaviour to prevent weight regain: restricting food, purging, or excessive exercise, typically driven by fear of weight gain.
Low weight or shape is central to self-evaluation, or the person sees their weight as normal or even too high.

Features

Most common in young women, typically starting in the mid-teens, but anyone of any age or sex can be affected (NHS).
WHO estimated 18 million people had eating disorders in 2023.
Physical signs include dizziness, hair loss, dry skin and missed periods (NHS); DSM-5 no longer requires amenorrhoea.
Risk factors include family history, criticism of eating or body shape, pressure to be slim (for example in ballet or modelling), perfectionism and anxiety (NHS).

If you are worried about your own eating or a friend's, talk to a trusted adult, your school counsellor or a doctor: eating disorders are treatable, and getting help early matters. If someone is in immediate danger, contact your local emergency services. Find A Helpline (findahelpline.com) lists free, confidential helplines in many countries.

Worked example

Calculate the BMI of an adult who weighs 45 kg and is 1.65 m tall, and decide which DSM-5 severity level applies.

BMI = weight / height² = 45 / 1.65² = 45 / 2.7225 = 16.53.
16.53 is between 16 and 16.99, so DSM-5 severity would be moderate (if criteria A to C are met).
ICD-11's cut-off of below 18.5 is also met.

Answer: BMI 16.5: moderate severity (DSM-5).

Key idea: DSM-5: restriction causing significantly low weight, intense fear of weight gain, disturbed body image; restricting or binge-eating/purging type; severity by BMI (mild 17+, extreme under 15). ICD-11: BMI below 18.5 as a common cut-off. Most common in young women, starting mid-teens.

Check yourself

An adult weighs 50 kg and is 1.70 m tall. Calculate their BMI to 1 decimal place.
Show answer
17.3 kg/m². 50 / 1.70² = 50 / 2.89 = 17.3.
Under DSM-5, an adult with anorexia and a BMI of 15.5 would be classed as
- mild
- moderate
- extreme
- severe
Show answer
severe. 15 to 15.99 is severe.
Which is a DSM-5 criterion for anorexia nervosa?
- Amenorrhoea for three months
- Intense fear of gaining weight or becoming fat
- A BMI over 25
- Hearing voices
Show answer
Intense fear of gaining weight or becoming fat. Criterion B. Amenorrhoea was removed in DSM-5.
What BMI does ICD-11 commonly use as the cut-off for significantly low body weight in adults? Give the number.
Show answer
18.5. Below 18.5 kg/m².
What are the two DSM-5 subtypes of anorexia nervosa?
- Restricting type and binge-eating/purging type
- Mild type and severe type
- Positive type and negative type
- Childhood type and adult type
Show answer
Restricting type and binge-eating/purging type. Based on behaviour over the last 3 months.
Explain one difference between DSM-5 and ICD-11 in diagnosing anorexia nervosa.
Show answer
ICD-11 gives a commonly used BMI cut-off of below 18.5 and allows rapid weight loss to replace low weight, whereas DSM-5 uses BMI to rate severity rather than as a single cut-off.. ICD-11 gives a low-weight cut-off; DSM-5 uses BMI bands for severity.

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Sources

Last updated 8 November 2026. Spotted a mistake? Tell us.