Managing psychiatric comorbidities of anorexia nervosa

The core psychiatric symptoms of anorexia nervosa (ie fear of gaining weight and body image disturbance) should be addressed with psychological therapy for anorexia nervosa.

Starvation causes psychiatric symptoms of anxiety, dysphoria, depressive symptoms and obsessional thinking, which should improve with nutritional replenishment. However, these symptoms may also be caused by a comorbid psychiatric disorder such as major depression or an anxiety disorder. Patients with anorexia nervosa should receive psychological therapy from a clinician that can differentiate starvation-related symptoms from a comorbid psychiatric disorder. Referral to a psychiatrist may be necessary.

If a comorbid psychiatric disorder is identified, refer to the management recommendations for the disorder. In choosing pharmacological treatment, consider the harm–benefit profile of the drug, in particular the:

• risk of drug interactions
• risk of adverse effects, see here for antidepressants and here for antipsychotics
• patient’s comorbidities.

Avoid antidepressants that cause QT-interval prolongation—patients with anorexia nervosa are at increased risk of cardiovascular sequelae because of possible electrolyte disturbances. Of the antidepressants, fluvoxamine, paroxetine and sertraline have a lower risk of QT-interval prolongation. For patients with a body mass index (BMI) less than 14 kg/m², start antidepressant treatment at half the usual starting dose; the dose adjustment schedule and maximum dose do not need to be reduced.

For management of acute agitation, see Approach to managing acute behavioural disturbance.

For ongoing agitation secondary to anorexia nervosa, a psychiatrist may use an antipsychotic or a benzodiazepine. Antipsychotics can reduce anorexic eating-related ruminations, psychological distress and may improve weight gain.