Nature Communications
June 24, 2026
Drummond E-Wen Mcculloch, Anders S. Olsen, Brice Ozenne et al.
A prominent theory of psychedelics is that they increase brain entropy. Thirteen studies have evaluated psychedelic effects on fMRI brain entropy, each applying a distinct measure. Here we evaluated these metrics in an independent 28-participant healthy cohort with 121 pre- and post-psilocybin fMRI scans. We assessed relations between brain entropy and objective and subjective psychedelic drug...
Journal of psychopharmacology (Oxford, England)
May 29, 2026
Kristoffer Brendstrup‐brix, Brice Ozenne, Patrick M. Fisher et al.
Patients with chronic cluster headache (CCH) suffer from poor sleep, which may impact their brain microstructure and parenchymal clearance of waste products. Psilocybin has shown promise for the treatment of CCH and has been linked to increased neuroplasticity with possible influences on brain microstructure. To investigate the effects of psilocybin on sleep, brain water diffusivity, and...
Research Square
October 10, 2025
Gitte M. Knudsen, Annette Johansen, Pontus Plavén-sigray et al.
Abstract Psychedelics such as psilocybin have been linked to enhanced neuroplasticity and symptom relief in affective disorders, but the neurobiological mechanisms and impact of environmen-tal context remain unclear. Here, we tested whether a single dose of psilocybin alters synap-tic density in healthy individuals and whether setting-dependent subjective experience shapes this effect. Fifteen...
medRxiv
June 18, 2025
Drummond E-Wen Mcculloch, Kristian Larsen, Annette Johansen et al.
preprint
In this study, we provide the first study to integrate molecular and functional neuroimaging during psychedelic drug effects in humans. Using simultaneous PET-MRI technology, we describe multiple brain actions of lysergic acid diethylamide (LSD) in healthy volunteers. We quantify the occupancy of LSD at cerebral serotonin 2A receptors and show that LSD increases global cerebral blood flow and...
Neurosci Appl
January 11, 2024
Drummond E-Wen Mcculloch, Matthias E. Liechti, Kim Pc Kuypers et al.
10 citations
Psychedelic drugs including psilocybin and LSD are undergoing clinical trials for a range of psychiatric and neurological conditions, and have particularly shown substantial promise in phase 2 studies of depression. In this article we outline key knowledge gaps that may be imperative for a successful implementation of psychedelic drugs as medicines as identified by members of the European...
Neuroscience Applied
2024
Drummond E-Wen Mcculloch, Juan Pablo Lopez, Christina Dalla et al.
2 citations
Classical psychedelic drugs, e.g., psilocybin and LSD, stimulate the serotonin 2A receptor (5-HT2AR) and have recently been intensely investigated for their clinical effects in various brain disorders. At the ECNP "New Frontiers meeting" in March 2023, scientific experts in psychedelics met to identify key knowledge gaps in the mechanism of action of psychedelics as investigated using...
medRxiv
July 3, 2023
Drummond E-Wen Mcculloch, Anders S. Olsen, Brice Ozenne et al.
20 citations
preprint
A prominent theory of psychedelics is that they increase brain entropy. Twelve studies have evaluated psychedelic effects on fMRI brain entropy quantifications, no findings have been replicated. Here we evaluated these metrics in an independent 28-participant healthy cohort with 121 pre- and post-psilocybin fMRI scans. We assessed relations between brain entropy and plasma psilocin, brain...
Neuroscience and Biobehavioral Reviews
July 1, 2022
Drummond E-Wen Mcculloch, Gitte Moos Knudsen, Frederick Streeter Barrett et al.
14 citations
Clinical research into serotonergic psychedelics is expanding rapidly, showing promising efficacy across myriad disorders. Resting-state functional magnetic resonance imaging (rs-fMRI) is a commonly used strategy to identify psychedelic-induced changes in neural pathways in clinical and healthy populations. Here we, a large group of psychedelic imaging researchers, review the 42 research...
Frontiers in Pharmacology
March 9, 2022
Drummond E-Wen Mcculloch, Maria Zofia Grzywacz, Martin Bruun Madsen et al.
91 citations
Psychedelic drugs such as psilocybin have shown substantial promise for the treatment of several psychiatric conditions including mood and addictive disorders. They also have the remarkable property of producing persisting positive psychological changes in healthy volunteers for at least several months. In this study (NCT03289949), 35 medium-high doses of psilocybin were administered to 28...
December 14, 2021
Drummond E-Wen Mcculloch, Maria Zofia Grzywacz, M. Madsen et al.
2 citations
preprint
Psychedelic drugs such as psilocybin are under investigation for the treatment of several psychiatric conditions. They also have the remarkable property of producing persisting positive psychological changes in healthy volunteers for at least several months. In this study, 35 medium-high doses of psilocybin were administered to 28 healthy volunteers (12 females). By the end of the dosing day,...
Journal of Psychopharmacology
June 30, 2021
Drummond E-Wen Mcculloch, Martin Bruun Madsen, Dea Siggaard Stenbæk et al.
79 citations
Background: Psilocybin is a psychedelic drug that has shown lasting positive effects on clinical symptoms and self-reported well-being following a single dose. There has been little research into the long-term effects of psilocybin on brain connectivity in humans. Aim: Evaluate changes in resting-state functional connectivity (RSFC) at 1 week and 3 months after one psilocybin dose in 10 healthy...