A small pilot study from the Centre for Psychedelic Research at Imperial College London indicates that psilocybin - the active ingredient in psychedelic 'magic mushrooms' - may have potential as a treatment for anorexia nervosa, when combined with therapy.
Anorexia nervosa is a serious eating disorder that changes how individuals experience their bodies and typically leads to dangerously low food intake and body weight. Current treatments are limited and often ineffective, so new approaches are urgently needed.
The pilot study, now published in the British Journal of Psychiatry, looked at 21 women who had lived with anorexia nervosa for an average of 11 years and had not found long-term success with any previous treatments. On average, participants were 32 years old and had a BMI of 16.4 kg/m2 (a healthy BMI is ≥ 18.5).All participants received three doses of oral psilocybin within a supportive therapeutic environment. The psilocybin sessions were supported with extensive talk therapy before and after dosing. This study did not include a control group.
Over six weeks, each participant received one 'assumed inactive' dose of psilocybin (1 mg, as a 'placebo') followed by two 'high doses' (25 mg) of psilocybin with two-week breaks in between. While participants knew they were receiving psilocybin, they didn't know which dose was being administered at each session. The first dose was intended to be small enough that participants would not feel any psychedelic effects. However, noticeable effects were reported by some participants.
To track the long-term impact of the treatment, participants were assessed at two weeks, three months, six months, and one year after their final session. Changes in the severity of their eating disorder symptoms and motivation to recover were measured. Their BMI was tracked for the first six weeks.
Psilocybin was found to be safe in this study, with headache and nausea the most common side effects. One participant chose to drop out after their second dose. Although there was no meaningful change in BMI, this was not unexpected given that this was only measured for a short period. However, average eating disorder scores were reduced at every follow-up, and nearly all participants (18/21) showed improvements two weeks after the final session. At 3 months, 48% of participants had scores comparable to someone without an eating disorder. Participants also reported an increased motivation to recover that lasted for one year.
Researchers emphasised that this was a small preliminary study without a drug-free comparison group. Results also indicated that the treatment was more beneficial for some than others.
While one participant suffered adverse events that resulted in hospitalisation during the follow-up period (suicide attempts at seven and nine months after dosing), this was carefully assessed by the researchers, study doctors and the Research Governance
and Integrity Team at Imperial College London, and not deemed related to the psilocybin intervention. These events should also be considered in the context that this patient population has a high base rate of suicidality.
Dr Hannah Douglass, a Postdoctoral Fellow at The University of Auckland, who led the study while completing her PhD at Imperial College London, said: "This study delivered a brief programme of psilocybin dosing and therapeutic support over a six-week period. Our results in individuals living with anorexia nervosa are encouraging, especially given that these participants had found previous treatments unsuccessful in maintaining their remission. However, further research is needed to assess how these findings might apply to a broader, more diverse population."
Senior Author and trial designer, Professor Robin Carhart-Harris, who is Honorary Professor at Imperial College London and Professor in Residence at the University of California San Francisco, said: "This was a pioneering trial with promising results that justify larger and more rigorous studies. In particular, the retention rate was excellent – something that is often a real challenge in anorexia nervosa treatment. This was despite the considerable commitment required from participants involving day-long dosing sessions and several sessions of psychotherapy."
Existing treatments for anorexia nervosa include SSRIs to treat associated depression and anxiety, and talking therapies such as Enhanced Cognitive Behavioural Therapy.
The researchers emphasise that psychedelic therapies must always be professionally designed and managed with additional psychological support, ideally from individuals with clinical experience of treating the relevant condition.
Dr David Erritzoe from the Department of Brain Sciences at Imperial College London said: "The findings bear out further research, but it's important to note that this was a particular dosing model carefully designed to support vulnerable participants with extensive psychological therapy alongside the psychedelic treatment. To be effective and safe, psychedelic treatments for individuals with complex mental health presentations, such as anorexia nervosa, should be given by trained clinicians in a supportive environment."
Jennifer Danby, a systemic psychotherapist and eating disorders specialist who was the lead therapist on the trial, said: "Having worked in the field of eating disorders for over 15 years it was encouraging to see that the trial, albeit with a very small cohort, provided an opportunity for individuals living with anorexia nervosa to approach treatment from a different angle. Anorexia often serves as a protective mechanism for people and we saw participants be able to explore their relationship with the illness and gain some new perspectives. By laying fertile ground for change, even minor adjustments can lead to promising change longer term."
The research was conducted at The National Institute for Health and Care Research Imperial Clinical Research Facility. This work was supported by the Nikean Foundation, Valor Equity Partners, and other funders of the Centre for Psychedelic Research, while Dr Douglass was supported by Imperial College London President's PhD Scholarship and Valor Equity Partners.
The work was also supported by the NIHR Imperial Biomedical Research Centre, a translational research partnership between Imperial College Healthcare NHS Trust and Imperial College London.
Psilocybin-Therapy for Adult Females with Anorexia Nervosa: A Pilot Study by Douglass and Spriggs, et al, is published in the British Journal of Psychiatry, DOI: https://DOI.org/10.1192/bjp.2026.10687
