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Kyle T Greenway

Centre for Psychedelic Research, Department of Brain Sciences, Imperial College London, London, UK. kyle.greenway@mcgill.ca.

9 papers in the library · 125 citations · publishing 2022-2026

Papers

Effect of psilocybin versus escitalopram on depression symptom severity in patients with moderate-to-severe major depressive disorder: observational 6-month follow-up of a phase 2, double-blind, randomised, controlled trial

EClinicalMedicine September 23, 2024 David Erritzoe, Tommaso Barba, Kyle T Greenway et al. 46 citations

In a clinical trial, psilocybin therapy showed comparable effectiveness to a common SSRI antidepressant for treating depression, with both treatments leading to significant reductions in depressive symptoms over a follow-up period. The findings suggest psilocybin may offer a viable alternative to standard antidepressant medication, though the study's design and sample size limit the strength of conclusions.

Longitudinal experiences of Canadians receiving compassionate access to psilocybin-assisted psychotherapy.

Scientific reports July 17, 2024 Sara de la Salle, Hannes Kettner, Julien Thibault Lévesque et al. 21 citations

A prospective longitudinal survey of eight Canadians with cancer who received legal psilocybin-assisted psychotherapy under Section 56 exemptions found significant improvements in anxiety, depression, pain, fear of COVID-19, quality of life, and spiritual well-being two weeks after the session. Attitudes toward death, medical assistance in dying, and desire for hastened death remained unchanged. Most participants found the sessions highly meaningful, though one reported a substantial decrease in well-being. These preliminary data suggest that real-world psilocybin-assisted psychotherapy can produce psychiatric benefits similar to those in clinical trials, but limited enrollment and negative experiences indicate a need for formal real-world evaluation programs.

Psychedelics and the ‘inner healer’: Myth or mechanism?

Journal of Psychopharmacology April 12, 2024 Joseph Peill, Miriam Marguilho, David Erritzoe et al. 16 citations

In a double-blind randomized controlled trial, 59 patients with depression received either a high (25 mg) or placebo (1 mg) dose of psilocybin. Those given the high dose reported stronger perceived 'inner healing' effects, and within that group, higher inner healer scores predicted greater improvement in depressive symptoms two weeks later. The findings suggest that the concept of an intrinsic healing mechanism activated by psychedelics merits further scientific investigation, though the idea remains scientifically nascent.

Intravenous ketamine for benzodiazepine deprescription and withdrawal management in treatment-resistant depression: a preliminary report.

Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology November 1, 2023 Nicolas Garel, Kyle T Greenway, Lê-Anh L Dinh-Williams et al. 10 citations

A course of six sub-anesthetic ketamine infusions over four weeks helped patients with treatment-resistant depression discontinue long-term benzodiazepine or z-drug use. Of 22 patients, 91% (20/22) successfully stopped all such medications by the end of the infusions, confirmed by urine tests. Fewer than 25% experienced significant worsening of anxiety, depression, sleep problems, or suicidality during withdrawal. Over a mean follow-up of one year, 64% (14/22) remained abstinent. These preliminary results suggest ketamine infusions may facilitate benzodiazepine deprescription even in patients with active depression and significant comorbidity.

Psychedelic medicine at a crossroads: Advancing an integrative approach to research and practice.

Transcultural psychiatry October 1, 2022 Gabriella Gobbi, Antonio Inserra, Kyle T Greenway et al. 9 citations

Psychedelics have been used by human societies for over 3000 years, primarily in religious and healing contexts. Recent research shows promising clinical benefits for some psychiatric disorders, but applying these consciousness-altering substances outside their traditional sociocultural settings raises concerns. The therapeutic mechanisms of psychedelics depend not only on neurobiology but also on psychological, social, and spiritual processes. Therefore, physicians and psychotherapists need training to guide patients through the experience, promoting positive outcomes and addressing side effects. Psychedelic therapies may lead to a new psychiatric paradigm integrating psychopharmacological, psychotherapeutic, and cultural interventions.

The Music for Subanesthetic Infusions of Ketamine randomised clinical trial: ketamine as a psychedelic treatment for highly refractory depression

The British Journal of Psychiatry June 18, 2025 Kyle T Greenway, Nicolas Garel, Lê-Anh L Dinh-Williams et al. 8 citations

In a clinical trial of ketamine combined with psychotherapy for severe treatment-resistant depression, 32 participants received six ketamine infusions with psychological support, either with or without music. Both groups showed large and sustained reductions in depression, anxiety, and suicidality at four weeks, fully maintained at eight-week follow-up. The ketamine experiences were highly emotional and mystical, comparable to those seen with psilocybin. Converging analyses suggested that mystical-like experiences contributed to the immediate and lasting antidepressant effects. Music did not enhance outcomes or psychedelic experiences.

The ketamine chameleon: history, pharmacology, and the contested value of experience.

Expert review of clinical pharmacology March 1, 2025 Danny Diep, Sara de la Salle, Julien Thibault Lévesque et al. 8 citations

Ketamine's subjective effects have been interpreted in three major ways since its 1962 synthesis: as dissociative, dream-like, or psychedelic, depending on the clinical context and dose. Biomedical frameworks often label its effects as dissociative or psychotomimetic, while psychedelic paradigms highlight potential therapeutic benefits. Factors such as language, dose, and environmental setting influence both the drug's effects and treatment outcomes. The authors argue that ketamine is best understood as a chameleon whose effects shift with context, rather than a tiger to be tamed. A nuanced, interdisciplinary approach is needed to maximize its clinical potential.

Ketamine for depression: a potential role in requests for Medical Aid in Dying?

International clinical psychopharmacology September 1, 2023 Nicolas Garel, Michka Nazon, Kamran Naghi et al. 7 citations

A Canadian patient with severe, prolonged treatment-resistant depression who was actively requesting Medical Assistance in Dying (MAiD) experienced remission after a course of intravenous ketamine infusions. This is the first reported case of any intervention yielding remission in a patient who would otherwise likely have been eligible for MAiD for depression. The case raises questions about evaluating MAiD requests for psychiatric disorders, particularly regarding the definition of irremediability—whether a patient lacks any reasonable prospect for recovery. The authors suggest that a trial of ketamine warrants consideration in similar cases.

Computational spirits: a neuroscientific account of psychedelic entity encounters.

Neuroscience of consciousness January 1, 2026 Jonas Mago, George Deane, Lars Sandved-Smith et al.

People under the influence of psychedelics often report encountering autonomous entities such as spirits, elves, or ancestors. A neurocomputational model, grounded in the active inference framework, explains these experiences by proposing that psychedelics reduce the predictability of sensory perceptions, leading the brain to interpret both internal and external perceptions as coming from non-self agents. The model synthesizes earlier theories including the entropic brain model, computational accounts of felt presence, and sensory attenuation theories of self-other discrimination. It aims to account for how the brain supports entity encounters and for the diversity and similarity of these experiences across cultural contexts.