Cited by 65Psychedelics and Drug StudiesMindfulness and Compassion InterventionsTreatment of Major Depression

Psychological flexibility as a mechanism of change in psilocybin-assisted therapy for major depression: results from an exploratory placebo-controlled trial

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Sloshower, Jordan, Zeifman, Richard J., Guss, Jeffrey, Krause, Robert, Safi-Aghdam, Hamideh, Pathania, Surbhi, Pittman, Brian, D’Souza, Deepak Cyril·2024·Scientific Reports

Abstract

Several phase II studies have demonstrated that psilocybin-assisted therapy shows therapeutic potential across a spectrum of neuropsychiatric conditions, including major depressive disorder (MDD). However, the mechanisms underlying its often persisting beneficial effects remain unclear. Observational research suggests that improvements in psychological flexibility may mediate therapeutic effects. However, no psychedelic trials to date have substantiated this finding in a clinical sample. In an exploratory placebo-controlled, within-subject, fixed-order study, individuals with moderate to severe MDD were administered placebo (n = 19) followed by psilocybin (0.3 mg/kg) (n = 15) 4 weeks later. Dosing sessions were embedded within a manualized psychotherapy that incorporated principles of Acceptance and Commitment Therapy. Depression severity, psychological flexibility, mindfulness, and values-congruent living were measured over a 16-weeks study period. Psychological flexibility, several facets of mindfulness, and values-congruent living significantly improved following psilocybin and were maintained through week 16. Additionally, improvements in psychological flexibility and experiential acceptance were strongly associated with reductions in depression severity following psilocybin. These findings support the theoretical premise of integrating psilocybin treatment with psychotherapeutic platforms that target psychological flexibility and add to emerging evidence that increasing psychological flexibility may be an important putative mechanism of change in psilocybin-assisted therapy for MDD and potentially, other mental health conditions.

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  • Specific traits of the psychedelic experience, such as acceptance-related experiences, mystical experiences, or reappraisal of negative emotion, are relevant mediators of the therapeutic outcomes of psychedelic-assisted psychotherapy.

    “Current research points toward specific traits of the psychedelic experience as relevant mediators of the therapeutic outcomes of PAP, such as acceptance-related experiences, the presence of mystical experiences, or the reappraisal of negative emotion (52–55).”

    From Ayahuasca-assisted meaning reconstruction therapy for grief: a non-randomized clinical trial protocol (2025) · cites this paper as [53]

    The Introduction (page unavailable) reports that mystical-type experiences have correlated with or partially mediated outcomes in some psilocybin studies, and identifies experiential acceptance as a potential mechanism. The Discussion (page unavailable) links increased acceptance with reduced depression severity, but cautions that the association does not establish causation and says the parent trial found no significant mystical-experience correlation. The paper does not address reappraisal of negative emotion as a mediator. (LLM, conf=0.86)

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Authors
Sloshower, J., Zeifman, R. J., Guss, J., Krause, R., Safi-Aghdam, H., Pathania, S., Pittman, B., & D’Souza, D. C.
Affiliations
  • Yale University (US)
  • NYU Langone Health (US)
  • New York University (US)
Corresponding author
Sloshower, Jordan
Venue
Scientific Reports
Published
2024-04-17
Volume
14
Issue
1
Pages
8833-8833
ISSN
2045-2322 (ISSN-L)
OpenAlex
W4394886406
Cited by
65
References
71
Citations by year
2026: 31 · 2025: 30 · 2024: 4
FWCI
32.47
Type
journal article
Language
en
Open access
Locations
  • Scientific Reports (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion)
Funders
Heffter Research Institute
Topics
  • Social Sciences › Psychology › Clinical Psychology › Psychedelics and Drug Studies
  • Social Sciences › Psychology › Clinical Psychology › Mindfulness and Compassion Interventions
  • Health Sciences › Medicine › Pharmacology › Treatment of Major Depression
Keywords
psilocybin-assisted therapy, major depressive disorder, psychological flexibility, mechanisms of change, acceptance and commitment therapy, mindfulness, experiential acceptance, psychedelic therapy, depression severity
MeSH terms
Depression, Major Depressive Disorder, Hallucinogens, Humans, Psilocybin, Acceptance and Commitment Therapy

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