Case 28: A teenager who wants to be as slim as a model

01The case

A 19-year-old woman is brought to a psychiatrist by her parents because she has lost a lot of weight. For six months she has eaten much less and followed a strict diet, wanting to become "as slim as a model". She goes to the gym often and exercises until she is exhausted. Even a small gain in weight makes her very anxious. Her periods stopped several months ago. Her body mass index is now 15, yet she keeps saying she is fat.

02Summary

Diagnosis

Anorexia nervosa, restricting type, with significantly low body weight.

What points to it

• Weight well below normal for her age (BMI 15), lost on purpose and kept low.
• Restricted eating and excessive exercise.
• An intense fear of gaining weight.
• A distorted body image: she believes she is fat when she is very thin.
• Amenorrhoea, a physical consequence of starvation. ICD-11 and DSM-5 no longer require it for the diagnosis.

What else it could be

Physical causes of weight loss (hyperthyroidism, diabetes, coeliac or inflammatory bowel disease, cancer) are excluded by examination and tests. Low mood and obsessional features are common in starvation and are reassessed once she is eating. A depressive episode can cause weight loss, but without the fear of fatness.

Management

• A physical risk assessment: pulse, blood pressure lying and standing, temperature, muscle strength, blood tests (electrolytes, phosphate, magnesium, glucose, liver function, full blood count) and an ECG. Ask about suicidal thoughts, since suicide accounts for a large share of deaths in anorexia.
• Most patients are treated as outpatients. Admission is decided by medical risk: a very low or fast-falling weight, a slow pulse, low blood pressure, low temperature, electrolyte disturbance, or suicide risk.
• With a BMI under 16 she is at high risk of refeeding syndrome, so feeding starts carefully, with thiamine and vitamins, and phosphate, potassium and magnesium checked daily at first.
• Psychological treatment is the core. At 19 she would usually be offered individual eating-disorder therapy such as CBT for eating disorders, with her family involved; for those under 18, anorexia-focused family therapy comes first. A dietitian is part of the team.
• Medication is not a treatment for anorexia. Antidepressants are used only for a separate depressive or anxiety disorder.

Outlook

Guarded. Anorexia has one of the highest mortality rates of any mental disorder, from physical complications and from suicide. With treatment, roughly a third recover fully, a third partly, and a third have a chronic course. Relapse is common in the first year.