Anorexia Nervosa

Relatively uncommon — prevalence is no more than 0.5% in women over 15, and substantially lower in men.

Diagnosis

• A relentless pursuit of thinness, causing weight loss or failure to gain weight during growth.
• Refusal to maintain a normal body weight, with an extreme fear of gaining weight or becoming fat.
• Physiological effects of starvation — amenorrhoea (in women), bone loss.
• Some patients also binge eat and/or use extreme weight-control behaviours (self-induced vomiting, laxative abuse).

Management

The guiding principles are, in order: restore a normal weight for height and age, then identify and address contributing family and personal problems. A multidisciplinary approach is needed — individual and family therapy (family therapy improves outcomes in adolescents still living at home), dietary advice, and pharmacotherapy where indicated.

Comorbid anxiety and depression are common, including depression secondary to starvation itself — this usually responds to nutritional restoration plus psychological treatment. Checking for physical complications (e.g. hypokalaemia, dehydration) is mandatory and can be lifesaving.

Prognosis: anorexia nervosa is potentially fatal, with significant mortality and morbidity. At 5 years: roughly 40% make a good recovery, 40% remain symptomatic with limited disability, and 20% remain severely symptomatic with chronic disability. Outcomes are notably better with early treatment and in children/adolescents — so consider specialist referral even before weight loss is marked. Families are commonly disrupted by the illness and need their own support and advice.

Pharmacotherapy

Antidepressants are appropriate for persistently depressed mood with neurovegetative features (late insomnia, diurnal mood variation, anhedonia) and depressive cognitions (guilt, hopelessness, worthlessness). Because of increased cardiovascular risk in anorexia nervosa (including QTc prolongation), start at half the usual dose and prefer agents with a low cardiovascular adverse-effect burden; TCAs and irreversible non-selective MAOIs should rarely be used.

Antipsychotics — low-dose (e.g. olanzapine 2.5–5 mg daily, or quetiapine/ amisulpride) may help extreme agitation, anorexic ruminations, and psychological distress, with some evidence for improved weight gain — but trial evidence is mixed, so use cautiously and only under specialist supervision.

Osteopenia — vitamin D and dietary calcium are recommended but are probably insufficient alone to reverse established bone loss; HRT and/or bisphosphonates may be considered in selected cases via specialist referral, though efficacy is unclear.

Refeeding — supplement iron, B-group vitamins, and zinc where deficient or during increased nutritional demand. Life-threatening hypophosphataemia can occur at the start of refeeding — give B-group vitamins, magnesium, and calcium prophylactically, plus electrolytes as needed, and ensure sufficient fat/protein in the refeeding diet.

Potassium — hypokalaemia (and consequent arrhythmia) is an important complication of purging/self-induced vomiting; potassium replacement can be lifesaving.