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
August 13, 2024
Oliver Rumle Hovmand, Dea Siggaard Stenbæk, M. Madsen et al.
9 citations
Background: Psychedelic substances reliably induce marked altered states of consciousness (ASC), which may be important for lasting effects and clinical outcomes of psychedelic intervention. Several instruments are available to measure the acute psychedelic experience, of which the Five Dimensional Altered States of Consciousness Questionnaire (5D-ASC) is commonly used. The questionnaire can be...
European Neuropsychopharmacology
August 9, 2024
Friederike Holze, M. Madsen, Claus Svarer et al.
16 citations
The serotonin 2A (5-HT2A) receptor is an important target for drug development and the main receptor through which classical psychedelics elucidate their hallucinogenic effects. The 5-HT2A receptor antagonist ketanserin has frequently been used as a tool to block the receptor. Here, we establish the dose-occupancy relation of ketanserin and the cerebral 5-HT2A receptor in healthy participants...
Journal of Psychoactive Drugs
January 15, 2024
Oliver Rumle Hovmand, Mathias Ebbesen Jensen, Tobias Søgaard Juul et al.
6 citations
Research suggests positive changes in both well-being and psychiatric symptoms following a psychedelic experience. One explanation may be the ability of psychedelic compounds to occasion mystical-type experiences. The Revised Mystical Experiences Questionnaire (MEQ30) is designed to assess the intensity and quality of such experiences. We examined the validity, reliability, and factor structure...
Headache The Journal of Head and Face Pain
2024
Anja Sofie Petersen, Inger Marie Sørensen, Harald Schiønning et al.
29 citations
Abstract Objective To evaluate the feasibility and prophylactic effect of psilocybin as well as its effects on hypothalamic functional connectivity (FC) in patients with chronic cluster headache (CCH). Background CCH is an excruciating and difficult‐to‐treat disorder with incompletely understood pathophysiology, although hypothalamic dysfunction has been implicated. Psilocybin may have...
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...
Neuroimage
October 27, 2022
Anders Lykkebo-Valløe, Brice Ozenne, Sophia Armand et al.
44 citations
Our findings suggest that the acute perceptual psychedelic effects induced by psilocybin may stem from drug-level associated decreases in the occurrence and duration of lateral and medial frontoparietal connectivity motifs. We apply and argue for a modified approach to modeling eigenvectors produced by LEiDA that more fully acknowledges their underlying structure. Together these findings...
Frontiers in Psychology
October 5, 2022
Anna Søndergaard, Brice Ozenne, Sophia Armand et al.
35 citations
Background Psilocybin-induced mystical-type experiences are associated with lasting positive psychological outcomes. Recent studies indicate that trait mindfulness is increased 3 months after psilocybin intake, preceded by decreases in neocortical serotonin 2A receptor (5-HT 2A R) binding. However, the association between psilocybin-induced mystical-type experiences and subsequent changes in...
medRxiv
July 10, 2022
M. Madsen, Anja Sofie Petersen, Dea Siggaard Stenbæk et al.
5 citations
preprint
Abstract Chronic cluster headache (CCH) is an excruciating disorder of unknown pathophysiology, but hypothalamic dysfunction has been implicated. CCH is difficult to treat but on a case-basis, the psychedelic compound psilocybin is said to have beneficial effects. In this first-ever clinical trial ( NCT04280055 ), we evaluate in a small open-label study of CCH patients the feasibility and...
medRxiv
December 17, 2021
Anders S. Olsen, Anders Lykkebo-Valløe, Brice Ozenne et al.
4 citations
preprint
Abstract Background Psilocin, the neuroactive metabolite of psilocybin, is a serotonergic psychedelic that induces an acute altered state of consciousness, evokes lasting changes in mood and personality in healthy individuals, and has potential as an antidepressant treatment. Examining the acute effects of psilocin on resting-state dynamic functional connectivity implicates network-level...
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,...
Social Cognitive and Affective Neuroscience
April 23, 2021
Maja Rou Marstrand-Joergensen, M. Madsen, Dea Siggaard Stenbæk et al.
20 citations
Evaluating associations between the five-factor personality domains and resting-state functional connectivity networks (e.g. default mode network, DMN) highlights distributed neurobiological systems linked to behaviorally relevant phenotypes. Establishing these associations can highlight a potential underlying role for these neural pathways in related clinical illness and treatment response....
Journal of Psychopharmacology
October 8, 2020
Dea Siggaard Stenbæk, M. Madsen, Brice Ozenne et al.
81 citations
Background: Psilocybin is a serotonergic psychedelic with psychoactive effects mediated by serotonin 2A receptor (5-HT2AR) activation. It produces an acute psychedelic altered state of consciousness with a unique phenomenology that can be temporally characterized by three intensity phases: onset of psychoactive effect, a peak plateau and return to normal consciousness. Aims: We evaluated...
European Neuropsychopharmacology
March 4, 2020
M. Madsen, Patrick M. Fisher, Dea Siggaard Stenbæk et al.
189 citations
A single dose of the serotonin 2A receptor (5-HT2AR) agonist psilocybin can have long-lasting beneficial effects on mood, personality, and potentially on mindfulness, but underlying mechanisms are unknown. Here, we for the first time conduct a study that assesses psilocybin effects on cerebral 5-HT2AR binding with [11C]Cimbi-36 positron emission tomography (PET) imaging and on personality and...
Neuropsychopharmacology
March 8, 2019
M. Madsen, Patrick M. Fisher, Daniel Burmester et al.
21 citations
correction
The original version of this article contained an error in the labelling of Figures 2 and 3. While the captions and figures themselves are correct, in order to correspond with the in-text references, they have now been re-numbered in both the PDF and HTML versions of the article.
Neuropsychopharmacology
January 26, 2019
M. Madsen, Patrick M. Fisher, Daniel Burmester et al.
505 citations
The main psychedelic component of magic mushrooms is psilocybin, which shows promise as a treatment for depression and other mental disorders. Psychedelic effects are believed to emerge through stimulation of serotonin 2A receptors (5-HT2ARs) by psilocybin's active metabolite, psilocin. We here report for the first time the relationship between intensity of psychedelic effects, cerebral 5-HT2AR...
Human Brain Mapping
January 11, 2019
Dea Siggaard Stenbæk, Sara Kristiansen, Daniel Burmester et al.
11 citations
Abstract Recent research found lasting increases in personality trait Openness in healthy individuals and patients after administration of the serotonin 2A receptor (5‐HT 2A R) agonist psilocybin. However, no studies have investigated whether 5‐HT 2A R availability as imaged using positron emission tomography (PET) is associated with this trait. In 159 healthy individuals (53 females), the...