Psilocybin as a potential treatment for anorexia nervosa in young people

A research team from Lund University in Sweden has published the full study protocol in PLOS ONE for the so-called psiAN study: a Phase IIa, open-label, randomised and controlled trial investigating whether psilocybin, combined with psychological support, is safe and feasible in adolescents and young adults with recurrent anorexia nervosa (AN).
This article does not yet describe any results; it is a pre-published research protocol, intended to provide transparency regarding the study design before the actual data are collected and analysed.

Why anorexia nervosa, and why psilocybin?

Anorexia nervosa has the highest mortality rate of all psychiatric disorders, and around one in five people with AN develop a severe, long-term course of the illness.
Relapse following recovery is common: around 30% within 1 to 2 years, and 40 to 50% in the longer term. There are currently no authorised medicines For the core symptoms of AN, only psychological and nutrition-based treatments.
Psilocybin is being investigated because it may act on mechanisms that sustain AN, such as cognitive rigidity, compulsive behaviour and emotional avoidance – the same processes that also play a role in depression and addiction, areas in which psilocybin has previously shown promising results.
Animal studies support this: in an animal model of anorexia, a single dose of psilocybin improved weight maintenance and cognitive flexibility in female rats, with effects mediated primarily via the 5-HT1A receptor.

Study design

Participants are aged between 16 and 35, have a DSM-5 diagnosis of AN and have previously achieved at least partial weight recovery (BMI ≥ 17), followed by a relapse.
They are randomised on a one-to-one basis to two conditions: two doses of 25 mg psilocybin with structured psychological support plus standard care (treatment as usual, TAU), or TAU only.
Participants in the control group will still be given the opportunity to receive psilocybin treatment after 6 months.
Due to the strong subjective effects of psilocybin, glare cannot be prevented in this study, which the researchers also explicitly identify as a methodological limitation.

What exactly is being measured?

The primary outcome measure is safety and tolerability: side effects, psychiatric monitoring and medical parameters.
Secondary outcome measures include changes in eating disorder symptoms, relapse measures, mood, well-being and personality traits, followed up to 12 months after the start.
In addition, the study contains two interesting exploratory, neurobiological measurements: functional MRI (fMRI) scans on a high-powered 7 Tesla scanner, to examine changes in brain connectivity during tasks such as a reward processing task and a task involving high-calorie food cues, and measurements of BDNF (brain-derived neurotrophic factor) in the blood, a protein that plays a role in brain plasticity and learning processes.

The treatment itself

Participants in the treatment group receive two dosing sessions 25 mg of psilocybin, administered four weeks apart, each session supervised by two trained therapists in accordance with a set protocol: preparatory sessions beforehand, non-directive support during the session itself, and several integration sessions afterwards.
Each participant must also have a fixed support person identify a person (a parent, partner or close friend) who can provide practical and emotional support in the period following the session, drawing on the role that those closely involved already play in family-centred therapy for AN.

Cautious admission of minors

A striking and carefully considered aspect of this protocol is the phased roll-out 16- and 17-year-olds: they will only be admitted once a safety committee has first assessed the data of the adult participants (aged 18–35).
In the case of minors, consent is required from both the participant themselves and both their legal guardians.
The researchers point out that categorically excluding adolescents from this type of research is not ethically neutral either, particularly as AN usually develops during the teenage years and a longer period without treatment is associated with a poorer prognosis.

Status and funding

Recruitment of participants has been underway since 1 March 2026 and is due to be completed in October 2027. The 12-month follow-up data collection period will continue until October 2028, after which results are expected from 2029 onwards.
The study is primarily funded by Norrsken Mind, with additional support from Region Skåne, the Swedish government and various research funds. The authors report no conflicts of interest.

Addition

This is not yet a results-based study, but the protocol itself is worth following, as it is one of the first controlled trials to specifically investigate psilocybin in adolescents is investigating people with an eating disorder, a group that has, until now, almost always been excluded from psychedelic research.
An earlier, smaller Phase 1 study involving adult women with AN had already shown that a single 25 mg dose of psilocybin was safe and well tolerated, with only mild and transient side effects, and that most participants wished to take part in a second session.
In that same earlier trial, two out of ten participants experienced the resurfacing of previously dissociated traumatic memories during the session, which was later associated with clinically significant improvement – a sign that trauma processing may play an important role in the recovery from AN through psilocybin.
Furthermore, the combination of fMRI and BDNF measurements makes this study interesting from a neuroscientific perspective: if the research team can demonstrate that psilocybin actually alters the overactive, rigid brain circuits associated with AN, this would provide a concrete mechanistic explanation as to why this treatment might work for this specific patient group.

Source: Sjöström D, Schau Rybäck O, Claesdotter Knutsson E, Kajonius P, Jensen Sondén O, Carlbring P, Björkstrand J, Movahed Rad P. "Study Protocol for 'Exploring the safety and therapeutic potential of psilocybin in the treatment of anorexia nervosa in adolescents and young adults'." PLoS One. 30 June 2026;21(6):e0352246. doi: 10.1371/journal.pone.0352246. Clinical trial: NCT07169747.