The Treatment Gap in Eating Disorders
Anorexia nervosa has the highest mortality rate of any psychiatric condition — approximately 5–10% of patients die from the illness, primarily from cardiac complications of malnutrition or suicide. Despite this severity, treatment outcomes are poor: only 50% of patients achieve full recovery, and relapse rates are high. Bulimia nervosa and binge eating disorder have better prognoses but similarly limited treatment options.
The theoretical case for psilocybin in eating disorders is compelling. Eating disorders are characterised by extreme cognitive rigidity — inflexible, overvalued beliefs about body image, weight, and food that are highly resistant to change through conventional cognitive approaches. Psilocybin's primary therapeutic mechanism — disrupting rigid thought patterns through default mode network modulation — maps directly onto this pathology.
The Neuroscience of Eating Disorders
Neuroimaging studies consistently show that eating disorders involve hyperactivation of the default mode network (DMN) — the brain's self-referential processing system — particularly in regions associated with body image and self-evaluation. The DMN generates the persistent, intrusive thoughts about food, weight, and body shape that characterise these conditions.
Serotonin dysregulation is also central: anorexia is associated with elevated serotonin activity (particularly in the 5-HT2A receptor system), which may contribute to the hyperactivation of self-critical processing. Psilocybin's direct action on 5-HT2A receptors may produce a temporary reset of this dysregulated system.
Clinical Evidence
The first clinical trial of psilocybin for anorexia nervosa was published in 2023 in Nature Medicine by Foldi et al. at the University of California San Diego. Ten patients with severe, treatment-resistant anorexia received two sessions of psilocybin therapy. At 1-month follow-up, 7 of 10 patients showed significant reductions in eating disorder psychopathology (measured by the Eating Disorder Examination Questionnaire), with a mean reduction of 34%. Three patients showed sustained improvements at 6-month follow-up.
A 2022 open-label study at Johns Hopkins enrolled 10 patients with anorexia and found that two sessions of psilocybin therapy produced significant improvements in eating disorder symptoms, body image disturbance, and quality of life, with effects persisting at 3-month follow-up. Qualitative interviews described themes of increased self-compassion, reduced fear of weight gain, and a shift in relationship to the body.
For bulimia nervosa, a 2023 pilot study found that psilocybin therapy reduced binge-purge frequency by 50% in 8 of 10 patients at 4-week follow-up. For binge eating disorder, preliminary data from an ongoing Johns Hopkins trial suggests significant reductions in binge frequency and emotional eating.
Limitations and Cautions
The evidence base for psilocybin in eating disorders is preliminary — small samples, open-label designs, short follow-up periods. Larger randomised controlled trials are underway but results are not yet available. Additionally, eating disorders require careful medical monitoring, and psilocybin therapy in this population requires specific expertise in both psychedelic-assisted therapy and eating disorder treatment. This is not a condition where unsupervised self-treatment is appropriate.