Psilocybin Shows Early Promise for Anorexia Nervosa

The psychedelic psilocybin may have a role in the treatment of anorexia nervosa (AN), an eating disorder that is notoriously difficult and costly to treat.

In a very small phase 1 trial of 10 women with AN, a single 25-mg dose of psilocybin coupled with psychological support, was safe and well-tolerated and decreased eating-disorder behaviors in some of the participants.

Stephanie Knatz Peck, PhD, and colleagues with the Eating Disorders Treatment & Research Center, University of California San Diego, write that the “robust response” in a subset of women after a single dose of psilocybin is “notable,” given that currently available treatments for adult anorexia result in only modest improvements in symptoms and often focus on weight and nutritional rehabilitation without adequately addressing underlying psychopathology.

However, given this was a small, phase 1, open-label feasibility study, these effects are “preliminary and inconclusive,” they caution.


The study was published online July 24 in Nature Medicine.


Meaningful Experience

The 10 women in the study met DSM-5 criteria for AN or partial remission of AN. They were between age 18 and 40 years with a mean BMI of 19.7 kg/m2.

Following the single 25-mg dose of psilocybin, no clinically significant changes were observed in ECG, vital signs, laboratory values, or suicidality. 

All adverse events were mild and mirrored typical psilocybin-associated symptoms such as transient headache, nausea, and fatigue.

Psilocybin was associated with reduced levels of anxiety and preoccupations surrounding food, eating, and body shape at the 1-month follow-up.

Weight concerns decreased significantly at the 1-month (= .036, Cohen’s d = .78) and 3-month (P = .04, d = .78) follow-up, with a medium to large effect.

Shape concerns significantly decreased at 1-month follow-up (= .036, d = .78) but were no longer significant at 3-month follow-up (= .081, d = .62).


Four of the 10 women (40%) had clinically significant reductions in eating disorder scores at 3 months, which qualified for remission from eating-disorder psychopathology. 


However, the researchers caution, that the effects on eating disorder psychopathology were “highly variable.”


On average, changes in BMI were not significant during the 3 months following psilocybin treatment. However, five women had an increase in BMI at 3 months, ranging from 0.4 to 1.2 kg/m2.


Overall, the psilocybin experience was regarded as meaningful by participants; 80% endorsed the experience as one of the top five most meaningful of life; 90% endorsed feeling more positive about life endeavors; and 70% reported experiencing a shift in personal identity and overall quality of life.


The vast majority of women (90%) felt that one dosing session was not enough.

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