Background
Anorexia Nervosa (AN) is a major health problem with one of the highest mortalities and treatment costs of any psychiatric condition. Cognitive behavioural therapy (CBT) is currently the most widely used treatment for AN in adults but provides remission rates ≤ 50%. Treatment drop-out is exceedingly high and those that persevere with treatment often relapse, causing increased risk of morbidity and mortality. There is an urgent need to find new interventions, especially as there are no approved pharmacological treatments for AN. Ideally, new treatments would target treatment-resistance and to decrease the chronicity associated with the disorder. Over the past two decades, emerging research into classic psychedelic substances (lysergic diethylamide acid (LSD), 5-Methoxy-N,N-Dimethyltryptamine (5-MeO-DMT), N,N-Dimethyltryptamine (DMT) and psilocybin), indicates that marked reductions in anxiety and depression-like symptoms, and lasting improvement in mental health, can follow from one or two exposures to these psychedelic substances. Anxiety and depression are the most prevalent co-morbid psychiatric symptoms in AN. Here we suggest that classic psychedelics, particularly psilocybin, have the potential to normalize dysfunctional neurobiological systems in AN and provide a novel treatment intervention that is worthy of consideration, particularly for treatment-resistant patients.