Psilocybin for Eating Disorders: Evidence, Trials & How It Works

Anorexia nervosa is the most fatal psychiatric disorder — with no FDA-approved pharmacological treatments and recovery rates below 50%. A growing body of evidence now suggests psilocybin may address the cognitive rigidity that standard therapies cannot reach. Here's what the Phase 1 data, active Phase 2 trials, and preclinical research show.

What the Research Shows

Anorexia nervosa (AN) has the highest mortality rate of any psychiatric disorder. Mortality is approximately 11–18 times higher than the general population, around 5% of patients die within 4 years of diagnosis, and the suicide rate is reported to be up to 56 times the global average (Imperial College London, 2021). Despite this severity, there are no FDA-approved pharmacological treatments that reverse AN's core symptoms, fewer than half of patients achieve recovery, and relapse approaches 50% (Kaye & Bulik, JAMA Psychiatry, 2021).

Binge eating disorder (BED) is the most prevalent eating disorder, affecting an estimated 2–3% of the US population, yet effective pharmacological options remain minimal. Fluoxetine is the only FDA-approved medication for bulimia nervosa; nothing is approved for AN or BED.

This profound treatment gap has driven researchers to investigate psilocybin — a compound that, in depression and OCD, has shown the ability to break rigid thought patterns through a mechanism that may be directly relevant to eating disorder neurobiology.

How Psilocybin May Help Eating Disorders

Understanding psilocybin's potential requires understanding what eating disorders — particularly AN — actually are at a neurobiological level. AN is not simply about food. It is a disorder of cognitive rigidity: the brain's inability to shift attention, challenge rigid beliefs about body image, and adapt behaviours in response to new information. This is the same cognitive inflexibility that characterises OCD, and the overlap is not coincidental — AN and OCD share neural substrates in the orbitofrontal cortex and striatal circuits.

The serotonin connection

Eating disorders are associated with serotonin dysregulation, particularly involving 5-HT2A receptors — the primary target of psilocybin. Individuals with AN show reduced 5-HT2A receptor activity in the prefrontal cortex and altered serotonin binding in the anterior cingulate cortex and insula — regions governing emotional regulation, interoception (awareness of bodily sensations), and the sense of self. Psilocybin's agonism at 5-HT2A receptors in these regions may help restore impaired signalling (MDPI Brain Sciences review, 2025).

Three proposed mechanisms

• Neuroplasticity window: Psilocybin opens a post-acute window of heightened neuroplasticity lasting approximately 2–4 weeks. For eating disorders — where rigid patterns of thought and behaviour have often been entrenched for years or decades — this window may allow new learning about food, body, and self to take hold in a way not possible during normal brain states.
• Default mode network disruption: The DMN — overactive in both depression and AN — generates self-referential rumination. In AN, this manifests as persistent intrusive thoughts about weight, body shape, and food. Psilocybin temporarily disrupts DMN connectivity, potentially interrupting these rigid loops.
• Cognitive flexibility restoration: Animal models directly support this. Psilocybin administration in activity-based anorexia rats improved reversal learning — the ability to update behaviour when circumstances change — through combined 5-HT1A and 5-HT2A receptor mechanisms (Conn et al., Molecular Psychiatry, 2024). This is the clearest direct mechanistic evidence to date.

Clinical Trials: What Has Been Done & What Is Active

1. Phase 1 Feasibility Study — UCSD / Compass Pathways (Peck et al., 2023) Early

The landmark study published in Nature Medicine (July 2023) was the first prospective clinical trial of psilocybin therapy in anorexia nervosa. Ten adult female participants meeting DSM-5 criteria for AN or partial remission AN (mean BMI 19.7 kg/m²) received a single 25 mg synthetic psilocybin dose (COMP360, Compass Pathways) with structured psychological support.

Primary outcomes (safety): No serious adverse events. No clinically significant changes in ECG, vital signs, laboratory values, or suicidality. Two participants experienced asymptomatic hypoglycaemia that resolved within 24 hours.

Secondary outcomes: Results were variable across participants, as expected in a feasibility study. Of those completing the Eating Disorder Examination (EDE), four showed clinically significant reductions in eating disorder psychopathology at one-month follow-up. BMI changes were not statistically significant on average. Qualitatively, 90% reported feeling more positive about life endeavours; 80% rated the session as one of the top five most meaningful experiences of their lives; 70% reported a shift in personal identity and quality of life. Notably, 90% felt one session was not enough, suggesting dose or protocol optimisation is needed.

The study was sponsored by Compass Pathways, the company developing COMP360 for a Phase 3 AN trial anticipated in 2026.

2. UCSF Phase 2 Trial — Refractory AN in Young Adults (NCT06399263, active) Early

A single-site Phase 2 trial at UCSF is currently enrolling young adults with refractory AN. The protocol includes three preparatory sessions, two psilocybin dosing sessions (20 mg followed by up to 25 mg, with integration sessions between), and three final integration sessions. Family member involvement is incorporated — one family member attends portions of the preparatory and integration sessions. The primary hypothesis is that psilocybin will increase cognitive flexibility and that this increase will predict long-term changes in cognitive rigidity, habitual eating, and exercise behaviours.

3. Imperial College London Pilot (active) Early

An ongoing pilot study at Imperial College London is assessing the feasibility, brain mechanisms, and preliminary outcomes of psilocybin-assisted therapy for AN. The trial incorporated extensive patient and public involvement (PPI), with 11 individuals with lived experience of AN informing the protocol design. This is one of several AN trials sponsored or co-funded through Compass Pathways' COMP360 program.

4. Binge Eating Disorder Pilot — University of Florida (Dallery et al., 2026) Early

Published in the Journal of Eating Disorders (January 2026), this open-label pilot of psilocybin-assisted therapy for BED found reductions in self-reported binge eating frequency across all participants, sustained through week 14. Improvements were also observed in depression, anxiety, and psychological inflexibility. fMRI analyses found preliminary signals of increased functional activation in the middle frontal gyrus and angular gyrus in response to food cues — suggesting changes in the neural evaluation of food. The study's small open-label design precludes causal inference but provides directions for future adequately powered trials.

5. Additional registered trials (systematic review, 2025)

A 2025 systematic review (Bevione et al.) identified six registered ClinicalTrials.gov studies of psilocybin in eating disorders. Beyond those above: one Baltimore-based trial (completed, results not yet published) used up to 4 sessions of 20–30 mg psilocybin in AN; one additional AN trial in London had estimated completion of June 2029; and one BED study in Gainesville, Florida (NCT05035927) completed enrollment. Results from completed but unpublished trials are anticipated in 2026.

Safety Considerations Specific to Eating Disorders

Psilocybin in eating disorder populations — particularly AN — requires additional safety precautions beyond standard psilocybin protocols, due to the physiological vulnerabilities associated with malnutrition. A 2024 narrative safety review (Downey et al., Journal of Eating Disorders) identified the key considerations:

Cardiac monitoring

Anorexia nervosa is associated with electrolyte abnormalities — particularly hypokalemia — which can prolong the QTc interval and create cardiovascular risk. Psilocybin causes transient increases in heart rate and blood pressure during sessions. All published AN trials screen for and correct electrolyte levels before dosing. The Nature Medicine Phase 1 trial found no clinically significant ECG changes, but cardiac screening is considered essential prior to any psilocybin session in AN populations.

Caloric and nutritional state

Medical stability — including adequate nutritional status — is a prerequisite in all AN trials. Severely underweight patients may face increased cardiovascular and metabolic risk from psilocybin's acute physiological effects. Weight stabilisation prior to psilocybin sessions is standard in all current protocols.

Psychological vulnerability

Eating disorders carry elevated suicide risk. All trials require thorough psychiatric screening and structured psychological support throughout the protocol. The psychedelic experience in AN may surface difficult material around body image and identity — making experienced psychological support critical.

Who May Be a Candidate

Based on published trial eligibility criteria, psilocybin for eating disorders has been studied in adults who broadly meet the following profile:

• Confirmed DSM-5 diagnosis of anorexia nervosa, binge eating disorder, or bulimia nervosa
• Adults aged 18+ (some UCSF trials include young adults from 16+)
• Medically stable — adequate nutritional and cardiovascular status for participation
• AN trials typically require at least one prior treatment attempt (CBT, FBT, or inpatient); BED trials have enrolled treatment-naive participants
• Ability and willingness to engage in preparatory and integration sessions (often 3–8 additional sessions around dosing)
• No personal or family history of psychosis, schizophrenia, or bipolar I disorder
• No current or recent SSRI use, or willingness to taper under clinical supervision — SSRIs blunt psilocybin's effects. See Microdosing on SSRIs

Access in 2026

Psilocybin has no FDA approval for any eating disorder indication and has not received Breakthrough Therapy designation for this use. Legal access pathways are limited but real.

Clinical trial enrollment

The primary legal access route. Search clinicaltrials.gov for "psilocybin eating disorder" or "psilocybin anorexia" to find currently recruiting trials. The UCSF trial (NCT06399263) and Imperial College London trial are the most advanced active AN studies. Participation is typically free; participants may receive compensation for time and travel.

Oregon and Colorado licensed programs

Oregon and Colorado's regulated psilocybin programs allow supervised adult use without a specific diagnosis requirement. Adults with eating disorder-related distress may legally access supervised sessions through licensed facilitators in these states. This is not a clinical treatment protocol, but the supervised setting and integration support built into Oregon/Colorado programs are consistent with the therapeutic approach being studied in trials. See Retreats and Legal Status for access pathways.

What to expect in a session

All psilocybin eating disorder trials use a preparation → dosing session → integration structure, with psychological support throughout. The dosing session itself is typically 6–8 hours. Integration sessions — often 3–5 follow-up meetings — are considered as important as the session itself. See the psilocybin therapy guide for the full 3-phase protocol.

Frequently Asked Questions

Key Takeaways

• → Anorexia nervosa is the most fatal psychiatric disorder, with no FDA-approved pharmacological treatments that reverse core symptoms — creating an urgent need for novel approaches.
• → The 2023 Nature Medicine Phase 1 trial established that 25 mg psilocybin is safe and tolerable in adults with AN, with some participants showing significant reductions in eating disorder psychopathology and 80% rating the session among the most meaningful of their lives.
• → The proposed mechanism — restoring cognitive flexibility via 5-HT2A-mediated neuroplasticity — is directly supported by preclinical data in anorexia rat models (Conn et al., Molecular Psychiatry, 2024).
• → Six clinical trials are now registered globally; Phase 2 trials are active at UCSF and Imperial College London; a Compass Pathways Phase 3 AN trial is anticipated in 2026.
• → Additional safety precautions are required in AN populations — electrolyte and cardiac screening before dosing. Medical stability is a prerequisite in all trials.
• → Psilocybin has no FDA approval for eating disorders. Legal access is via clinical trial enrollment or Oregon/Colorado supervised programs.