Safety, Therapeutic Potential, and Mechanisms of Two Psilocybin Doses, Administered With Psychological Support in Young Adults With Anorexia Nervosa

Background and Rationale Anorexia Nervosa (AN) is one of the most lethal psychiatric disorders, with mortality rates approximately five times higher than that of the general population. AN affects multiple organ systems due to severe weight loss and malnutrition and hence leads to a substantial decline in health-related quality of life. While psychotherapies have shown partial efficacy, data suggest that only 46% of patients recover within four years, and 20% remain chronically ill. Relapse rates exceed 50% among those who recover, underscoring the need for more effective treatments. Research suggests that several psychological factors, such as challenges in regulating emotions, black-and-white thinking, mental rigidity, and a limited capacity for mentalization may contribute to the persistence of severe, chronic anorexia nervosa. The age of onset for AN typically shows a bimodal distribution, peaking at 14 and 18 years of age, motivating the design of including patients as young as 16 years old in this study.

Psilocybin, a serotonergic psychedelic compound, primarily acts as an agonist of the 5-HT2A receptor, inducing profound effects on cognition, emotion, perception, and self-awareness. Although research on psilocybin remains limited, clinical trials across psychiatric disorders suggest its potential therapeutic benefit. For example personality changes such as increased openness, have been observed to persist up to a year following a single high dose. The inclusion of 16-17-year-olds in this study is particularly novel, as research on psychedelic therapy in adolescents and young adults remains scarce.

Emerging evidence highlights how psychedelics may benefit AN patients, such as enhanced serotonin signaling and cognitive flexibility. The ability of psychedelics to foster cognitive flexibility, a well-documented phenomenon, is considered a key factor in therapeutic processes. This is especially relevant for AN, where rigid thinking and behavior contribute to treatment resistance. One pilot study demonstrated that a 25 mg psilocybin dose, combined with psychological support, was well-tolerated by female AN patients with a body mass index (BMI) \>16. The study reported significant reductions in eating disorder symptoms at one month post-treatment, with only mild and transient adverse events.

Recent studies indicate that psilocybin induces significant changes in brain function and network organization across key regions. Notably, psilocybin disrupts connectivity in the default mode network by causing desynchronization across spatial scales. These findings suggest a neurobiological basis for psilocybin´s therapeutic effect. However, further research is needed to elucidate long-term effects, particularly in clinical context. Functional magnetic resonance imaging (fMRI) has demonstrated utility in detecting neuronal abnormalities in AN. This study's use of fMRI before and after psilocybin treatment will provide critical insights into the neurobiological impacts of psilocybin on AN.

Brain-Derived Neurotrophic Factor (BDNF) is a protein that plays a crucial role in neuroplasticity. Preclinical studies show that psilocybin promotes neuritogenesis and synaptic plasticity, potentially via increased cortical BDNF expression. Given that individuals with AN exhibit reduced serum BDNF levels, this study will assess changes in BDNF pre- and post-treatment to elucidate psilocybin's impact on neurobiological mechanisms. These insights may advance treatment optimization and efficacy predictions for AN patients.

Study Objectives Primary Objective is to assess the safety and tolerability of psilocybin 25 mg in young adults (16-35 years old) with anorexia nervosa. Secondary objectives include evaluating the efficacy of psilocybin with psychological support in reducing AN symptom compared to treatment as usual (TAU), investigate potential mechanisms of action through self-report questionnaires, neuroimaging and BDNF analysis, and conduct qualitative analysis of subjective experiences. Neuroimaging will investigate changes in brain resting state connectivity (measured by fMRI), and commonly used task-based fMRI paradigms. The task-based paradigms will involve food-related conditions, commonly used in the population (Celeghin et al., 2023; Bronleigh et al., 2022) as well as established paradigms involved in processing reward anticipation (Knutson et al., 2000; Ventorp et al 2022)

Trial Design and Procedures

This is a phase II, open-label, randomized controlled trial with two arms:

1. Active treatment arm; Two dosing sessions with psilocybin 25mg with psychological support alongside TAU. 2. Active comparator control arm; TAU only. The study will include 40 participants, 20 in each group. If the active treatment arm is determined to be safe, tolerable, and preliminarily effective during the follow-up assessment, participants in the control group will have the option to switch to the active treatment while maintaining their usual specialized care. The switch to psilocybin treatment will follow the same preparation, dosing, and integration protocols as outlined for the intervention group.

This design minimizes ethical concerns regarding withholding a potentially effective treatment. Participants will be randomly assigned (1:1) to either the intervention or control group. Block randomization stratified by age group (16-18 and 19-35 years) will ensure balanced representation.

Given the small sample size of 40 participants (20 per group), the statistical power to detect between-group differences is inherently limited, irrespective of blinding. As such, the trial is appropriately designed as a pilot study, with a primary focus on assessing safety, feasibility, and tolerability. To enhance interpretation, qualitative and neurobiological measures are also included. A formal power calculation was not conducted, in line with the exploratory nature of the study. The sample size was determined based on practical feasibility and aligns with current recommendations for early-phase trials of novel interventions. A post-hoc power analysis will be conducted to evaluate whether the sample size was sufficient to detect clinically meaningful changes in the primary outcomes.

Details on location and Data Collection Methods All procedures will be conducted at the University Hospital for Psychiatry, Baravägen 1, Lund, except the fMRI assessments which are performed at the The National 7 Tesla (7T) Facility in Lund. All assessments will be carried out by qualified personnel appointed by the principal investigator, including medical doctors, nurses, and psychologists. The National 7T Facility will appoint qualified personnel for fMRI assessment. The duration of the entire trial is from the first screening of the first patient to the last follow up of the last patient. For each patient participant, the duration of the trial is from the screening to the last follow up at week 52 (12 month). Patient rehospitalization and additional interventions data are collected in patient journal registers.

Pre-Study Activity Following ethical approval, a focus group will be conducted with patients with anorexia nervosa in two different groups, one aged 16-18 and one 19-35 years. The purpose is to provide study information, gather feedback on the clarity and ethical aspects of the protocol, and identify ways to improve potential benefit. Input from this focus group will inform study quality, recruitment materials, communication strategies and ethical aspects of psilocybin research experienced by the population. Any amendments based on this will be processed according to CTIS protocol.

Screening Phase Screening includes psychiatric and medical history, inclusion/exclusion criteria assessment, safety blood tests (glucose, liver, kidney), electrocardiogram (ECG), informed consent (with a 2-week consideration period), pregnancy test and urine toxicology (U-tox). The time from screening to the first psilocybin dose must not exceed 8 weeks, regardless of washout status. Potential participants will be screened by a psychiatric clinician appointed by the principal investigator to ensure eligibility and understanding of the study requirements.

Preparation Phase

Preparation Session 1 \& Baseline Assessment (Week -1):

Psychoeducation about psilocybin, breathing and relaxation techniques, rapport-building with therapists, and discussion of expectations and concerns.

Includes full baseline assessments (list provided as attachment to protocol: * Expectation of Treatment Scale (ETS-BF) * Readiness and Motivation Questionnaire (RMQ) * General Change Mechanisms Questionnaire (GCMQ) * Patient Health Questionnaire (PHQ-9) * Generalized Anxiety Disorder scale (GAD-7) * Eating Disorder Examination Questionnaire (EDE-Q ) * Columbia-Suicide Severity Rating Scale (C-SSRS) * Brief Psychiatric Rating Scale - Extended (BPRS+) * Life Satisfaction Scale (LS) * Positive and Negative Affect Schedule (PANAS) * Harmony in Life Scale (HILS) * Ten Item Personality Inventory (TIPI) * Honesty-Humility Scale (HH) Vital signs, ECG, fasting glucose, urine drug screening, fMRI, BMI, metric assessment of body size perception and blood sampling for BDNF and safety labs are also conducted.

Preparation Session 2 (Week 0): 7-10 days after Preparation 1, and 2-3 days before psilocybin dosing.

Dosing and Integration Phase Dosing Session 1 (Week 0): Psilocybin 25 mg under therapeutic support with ECG and blood pressure/pulse monitoring.

Integration Session 1 (Day after Dosing 1): Reflection, fMRI, blood sampling (including glucose, liver, kidney, BDNF), and reassessments with RMQ, GCMQ, PHQ-9, GAD-7, C-SSRS, BPRS+, LS, PANAS, HILS, TIPI, ECG and blood pressure/pulse. Psychedelic Experience related scales; Altered States of Consciousness Rating Scale (5D-ASC), Mystical Experience Questionnaire (MEQ-4), Meaningful Life Experience Rating (MLE).

Integration Session 2 (Week 1): Continued psychological integration support.

Integration Session 3 (Week 2-3): Summary of first dosing experience and preparation for second dosing.

Dosing Session 2 (Week 4): Second psilocybin 25 mg administration under identical conditions as first dosing session.

Integration Session 4 (Day after Dosing 2): Reflection, blood sampling (including glucose, liver, kidney, BDNF), and reassessments with RMQ, GCMQ, PHQ-9, GAD-7, C-SSRS, BPRS+, LS, PANAS, HILS, TIPI, ECG and blood pressure/pulse. Psychedelic Experience related scales; Altered States of Consciousness Rating Scale (5D-ASC), Mystical Experience Questionnaire (MEQ-4), Meaningful Life Experience Rating (MLE).

Integration Session 5 (Week 5-6): Final integration session and preparation for long-term follow-up.

Primary Endpoint (Week 8)

Includes full safety and outcome evaluations: * fMRI * blood sampling (including glucose, liver, kidney, glucose, BDNF) * Vital signs, ECG, U-tox * BMI * Metric assessment of body size perception * Adverse Event/Serious Adverse Event (AE/SAE) monitoring * Readiness and Motivation Questionnaire (RMQ) * General Change Mechanisms Questionnaire (GCMQ) * Patient Health Questionnaire (PHQ-9) * Generalized Anxiety Disorder scale (GAD-7) * Eating Disorder Examination Questionnaire (EDE-Q ) * Columbia-Suicide Severity Rating Scale (C-SSRS) * Brief Psychiatric Rating Scale - Extended (BPRS+) * Life Satisfaction Scale (LS) * Positive and Negative Affect Schedule (PANAS) * Harmony in Life Scale (HILS) * Ten Item Personality Inventory (TIPI) * Honesty-Humility Scale (HH)

Intensive Follow-Up Phase (Week 8-24)

Follow-up visits at Week 12, 16, and 20 include: * Eating Disorder Examination Questionnaire (EDE-Q ) * Columbia-Suicide Severity Rating Scale (C-SSRS) * Brief Psychiatric Rating Scale - Extended (BPRS+) * AE/SAE monitoring * BMI, blood pressu

• To evaluate the efficacy of two doses of psilocybin, administred with psychological support, in reducing AN symptoms compared to TAU, as measured by time to response, time to remission and time to relapse. [Срок оценки: Efficacy will be evaluated during the 12-month follow-up.]
• Assess potential mechanisms of action through neuroimaging (fMRI), before and after the two-dose psilocybin treatment, administered with psychological support [Срок оценки: fMRI will be preformed at baseline (week 0), after first dosing (week 1) and at primary endpoint (week 8).]
• Changes in serum brain-derived neurotrophic factor (BDNF) levels from before and after treatment with two doses of 25 mg psilocybin, administered with psychological support. [Срок оценки: BDNF samples will be taken at five key time points: (1) before treatment (baseline), (2) and (3) at first integration session after Psilocybin 25mg dosing, (4) at 8 weeks, and (5) during the 6-month follow-up.]
• To conduct a qualitative analysis of how participants, their relatives, and therapists experience and perceive the intervention [Срок оценки: Assessments will be preformed at different timepoints during the 12-month follow-up.]
• To assess changes in symtoms of depression before and after two-doses of psilocybin, administered with psychological support, in young adults with anorexia nervosa. [Срок оценки: Changes will be assessed at baseline and then repeatedly within the 12-month follow-up]
• To assess changes in symtoms of anxiety before and after two-doses of psilocybin, administered with psychological support, in young adults with anorexia nervosa. [Срок оценки: Changes will be assessed at baseline and then repeatedly within the 12-month follow-up.]
• To assess changes in eating disorder symptoms before and after two-doses of psilocybin, administered with psychological support, in young adults with anorexia nervosa. [Срок оценки: Changes will be assessed at baseline and then repeatedly within the 12-month follow-up.]
• To assess changes in suicidal ideation and behavior before and after two-doses of psilocybin, administered with psychological support, in young adults with anorexia nervosa. [Срок оценки: Changes will be assessed at baseline and then repeatedly within the 12-month follow-up.]
• To assess changes in psychiatric symptom severity before and after two-doses of psilocybin, administered with psychological support, in young adults with anorexia nervosa. [Срок оценки: Changes will be assessed at baseline and then repeatedly within the 12-month follow-up.]
• To assess changes in life satisfaction before and after two-doses of psilocybin, administered with psychological support, in young adults with anorexia nervosa. [Срок оценки: Changes will be assessed at baseline and then repeatedly within the 6-month follow-up.]
• To assess changes in positive and negative affect before and after two-doses of psilocybin, administered with psychological support, in young adults with anorexia nervosa. [Срок оценки: Changes will be assessed at baseline and then repeatedly within the 6-month follow-up.]
• To assess changes in harmony in life before and after two-doses of psilocybin, administered with psychological support, in young adults with anorexia nervosa. [Срок оценки: Changes will be assessed at baseline and then repeatedly within the 6-month follow-up.]