Clinical TrialSingle-armDepressive DisordersPsilocybinCompleted

Psilocybin-Assisted Treatment Naturalistic Observational Study: Mood and Personality Moderators (Irrmischer / Engelbregt, Netherlands 2025)

This unregistered trial (n=83) was an open-label, naturalistic observational study of psilocybin-assisted treatment for depression, anxiety, and PTSD in self-referred participants, which found that subjective experiences and demographic factors moderated improvements in mood and personality.

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Target Enrollment
83 participants
Study Type
interventional
Design
Non-randomized

Detailed Description

This synthetic trial has been added to our database because a psychedelic paper (about a clinical trial) references this trial, but no (live) registration can be found.

The study investigated the moderating factors of an individual psilocybin-assisted programme, which included intake, preparation, a single 25 mg psilocybin dose (administered via fresh truffle sclerotia), and integration. The cohort consisted of 83 self-referred participants, approximately 45% of whom had a prior or current psychiatric diagnosis. Researchers assessed changes in depression, anxiety, PTSD, and personality structures using standardised scales such as the PHQ-9, GAD-7, and PCL-5.

Results indicated that the treatment led to a reduction in symptoms of anxiety, depression, and PTSD, as well as a decrease in neuroticism over a three-month period. Additionally, increases were observed in personality traits of openness and conscientiousness. The study concluded that mystical-type experiences, emotional breakthroughs, and personal growth served as significant moderators for these positive clinical outcomes.

Study Arms & Interventions

Psilocybin-assisted treatment program

experimental

Individual psilocybin-assisted treatment program consisting of intake, preparation, dosing session, and integration. Dosing involves fresh truffle sclerotia equivalent to 25 mg psilocybin.

Interventions

  • Psilocybin25 mg
    via Oral• single dose• 1 doses total

    Administered via fresh truffle sclerotia; combined with preparatory therapy (1h online, 2h in-person, 1h practical) and integration therapy (2h in-person day after, 1h online 1 week later).

Study Details

  • Status
    Completed
  • Type
    interventional
  • Design
    Non-randomized
  • Target Enrollment83 participants
  • Timeline
    Start: 2020-01-01
    End: 2024-12-31
  • Compound
    Psilocybin
  • Topic
    Depressive Disorders

Locations

Netherlands

Related Publications

Open AccessindividualPrimary

Moderating factors in psilocybin-assisted treatment affecting mood and personality: A naturalistic, open-label investigation

In a naturalistic, open‑label study a single high dose of psilocybin with psychotherapy produced sustained reductions in depression, anxiety, PTSD symptoms and neuroticism, and increases in openness and conscientiousness at three months. The size of these benefits was moderated by participants’ subjective dosing experiences (mystical‑type experiences, emotional breakthrough and post‑treatment growth) and demographic factors, highlighting variables that may help optimise psilocybin‑assisted treatment.

Published
Journal
Psychopharmacology
Authors
Irrmischer, M., Puxty, D. J., Deijen, J. B., Engelbregt, H., Yildirim, B. O.