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expert reaction to Phase 1 study of psilocybin for anorexia

A phase 1 study published in Nature Medicine looks at the feasibility of psilocybin therapy for females with anorexia nervosa.


Dr Alexandra Pike, Lecturer in Mental Health, University of York, said:

“The authors report the results of a small Phase 1 clinical trial of psilocybin (the active ingredient in ‘magic mushrooms’) in 10 people with the eating disorder anorexia nervosa (though some participants were in partial recovery). Notably, Phase 1 trials are not designed to test the efficacy of an intervention on symptoms: instead, a Phase 1 study is performed to assess whether an intervention is safe and tolerable in a sample of the people it might be used in. In this small and self-selecting sample, there were no serious adverse events, but two participants experienced a brief period of low blood sugar. The changes found in eating disorder symptoms were very subtle, and only appeared in a few of the many questionnaires participants completed – in contrast to more unambiguous results in disorders such as major depressive disorder. Limitations include the fact that there was no control group, so any improvement might be a ‘placebo effect’, and were self-selecting, so may already have felt positive about psychedelics and expected psilocybin to work.

“Additionally, the protocol includes sessions with psychologists alongside the delivery of psilocybin, which may also have caused effects on symptoms. It is also worth noting that two authors (SKP and WHK) have financial and scientific relationships with COMPASS Pathways, the company which manufactures this form of psilocybin. In sum, this study is a first step in showing that psilocybin may be a safe treatment for those with anorexia nervosa, but we cannot conclude from this work that it will be effective in this chronic, complex illness.” 


Prof Michael Bloomfield, Professor of Psychiatric Neuroscience, UCL, said:

“Anorexia is a potentially life-threatening illness. Whilst there are effective treatments for anorexia including medicines and psychotherapies, there is an urgent need to develop new treatments. There is a lot of interest and hype around the use of psilocybin to potentially treat a range of different psychiatric conditions. This new small study is early stage research aiming to see whether psilocybin combined with a psychotherapy is safe in people with anorexia. The study was not designed to measure whether the experimental treatment was effective and there were no placebo conditions. This small study found that the experimental treatment was safe enough to warrant further research studies which should now take place. Whilst this is exciting news, we cannot yet say the psilocybin-assisted therapy will be helpful for patients suffering from anorexia. Treatment with psilocybin-assisted therapy for anorexia should not be taking place outside of research trials. Anorexia can be potentially life-threatening. People with anorexia and other eating disorders need access to highly specialised psychiatrist-led multidisciplinary teams. No one with anorexia or other eating disorders should attempt to self-medicate with psilocybin.”


Comments sent out by our colleagues at SMC Australia:

Dr Trevor Steward, Senior Research Fellow in the School of Psychological Sciences, University of Melbourne, said:

“This study represents an important first step towards determining how safe and well-tolerated psilocybin therapy is for adult patients with anorexia nervosa. It opens the door for the next phase of clinical trials to assess the effectiveness of psilocybin therapy in improving anorexia nervosa symptoms.

“Psilocybin therapy has provided glimmers of hope in other mental health disorders, notably by providing evidence that it can improve anxiety, cognitive flexibility, and self-acceptance for some people. These are all features of anorexia nervosa and the rationale for exploring psilocybin therapy as an option in the case of anorexia is strong. However, this study does not demonstrate that psilocybin therapy can be used to treat anorexia nervosa. Larger-scale clinical trials are a fundamental requirement to confirm whether psilocybin therapy can indeed be considered a viable treatment for anorexia nervosa. While these results show this psilocybin therapy is safe under controlled conditions, it’s essential not to let the hype around psychedelics outpace the scientific evidence. Continued research and caution are of the utmost importance to ensure we make informed decisions about the potential of psilocybin therapy in tackling this deadly illness.

“The field is only beginning to scratch the surface in terms of understanding how psilocybin impacts the brain and dedicated funding to exploring how it specifically acts to target anorexia nervosa symptoms is crucial to advancing this important avenue of research. As there are no approved medications available specifically for anorexia nervosa treatment, psilocybin therapy may prove to be a promising option, though additional research is needed to test this.”


Dr Claire Foldi, Senior Research Fellow at the Monash University Biomedicine Discovery Institute, said:

“This study in Nature Medicine reports that a single dose of psilocybin, administered in a tightly controlled setting and with specialised psychological support, was safe, well tolerated and acceptable for individuals with anorexia nervosa, in line with previous reports of psilocybin-assisted psychotherapy in other clinical populations.

“Novel treatment strategies are urgently needed for anorexia nervosa, which is associated with one of the highest mortality rates of any psychiatric condition, but until now there was concern of specific risks of adverse effects in these individuals based on the medical abnormalities of low body weight and cardiovascular complications.

“It’s important to recognise that while the effects of psilocybin therapy on eating disorder symptoms in this study were exploratory in nature and highly variable among the ten participants included, four individuals (40%) demonstrated clinically significant reductions in symptom presentation three months after the experience.

“A major limitation of this study, duly noted by the authors, was that it included a small, self-referred and therefore perhaps non-representative clinical sample. In addition, the lack of a control comparison precludes the possibility that an expectation of positive outcomes may have influenced these findings. These caveats aside, the results offer promise in the pursuit of larger, adequately controlled trials that will determine whether psilocybin-assisted psychotherapy could aid in the unmet need for effective treatment options for individuals suffering from anorexia nervosa.”


Associate Professor Gemma Sharp, Head of Body Image & Eating Disorders Research and Senior Clinical Psychologist, Monash University, said:

“It is exciting to see this research being undertaken. There are currently no approved pharmacological interventions for anorexia nervosa and these are very much needed to save lives!

“My own eating disorder patients have expressed interest in psilocybin therapy for a number of years and I am glad that there are gradually more opportunities for them to participate in research. Having said that, this published research is very preliminary. It involved only 10 women with anorexia nervosa, five in partial remission, and an average BMI in the normal weight range rather than underweight.

“Nevertheless, the research suggested that a single dose of psilocybin together with psychological support was safe, tolerable and acceptable. The number of people involved in the research was too small to thoroughly examine the impacts on eating disorders and broader mental health symptoms. However, the women generally reported improvements in their quality of life which is so important in eating disorder recovery.

“This research provides an important platform for larger-scale research. A crucial goal for future research is understanding exactly how psilocybin might assist people with anorexia nervosa (the biological mechanisms) as this will allow us as clinicians and researchers to optimise any treatment strategies.”



‘Psilocybin therapy for females with anorexia nervosa: a phase 1, open-label feasibility study’ by Stephanie Knatz Peck et al. was published in Nature Medicine at 16:00 UK time on Monday 24 July.




Declared interests

Prof Michael Bloomfield: “No conflicts.”

Dr Trevor Steward has declared he has no conflict of interest.

Dr Claire Foldi has not declared any conflicts of interest.

Dr Gemma Sharp has declared she has no conflicts of interest.

For all other experts, no reply to our request for DOIs was received.

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