European neuropsychopharmacology : the journal of the European College of Neuropsychopharmacology
September 1, 2021
Martin K Madsen, Dea S Stenbæk, Albin Arvidsson et al.
132 citations
Psilocybin, a novel therapeutic, is metabolized to psilocin, which alters brain function by engaging serotonin receptors. In fifteen healthy individuals, a psychoactive dose (0.2-0.3 mg/kg) reduced the integrity and segregation of brain networks, including the default mode network, while increasing connectivity between networks like the executive control and dorsal attention networks. These changes correlated with plasma psilocin levels and subjective drug intensity. The findings link psilocin's time course to shifts in brain functional architecture and subjective experience, offering insight into the neurobiological mechanisms of psychedelic effects and consciousness.
Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism
February 26, 2025
Kristian Larsen, Ulrich Lindberg, Brice Ozenne et al.
9 citations
Psilocybin, the active compound in magic mushrooms, reduces blood flow in the brain. In a study of 28 healthy volunteers, psilocybin decreased cerebral blood flow by about 11.6% at peak effect, while the serotonin blocker ketanserin had no significant effect. Psilocybin also constricted the internal carotid artery by 10.5%, whereas ketanserin did not. These findings suggest that psilocybin's effects on brain blood flow involve the serotonin 2A receptor and may help explain its therapeutic potential for conditions like depression.
Neuroscience Applied
December 30, 2023
Sophia Armand, Kristian Larsen, Martin K Madsen et al.
7 citations
The psychedelic drug psilocybin acutely reduces amygdala reactivity to angry faces in healthy individuals, while its subjective intensity is linked to reduced amygdala response to fearful faces. In 26 participants, fMRI scans showed that amygdala response to angry faces was significantly lower under psilocybin compared to baseline. No significant changes occurred for fearful or neutral faces. Higher subjective drug intensity was associated with weaker amygdala response to fearful faces, but plasma psilocin levels showed no such link. These findings align with prior work, suggesting psilocybin alters emotion processing in the brain, with potential implications for treating depression.
Cureus
January 29, 2025
Sorcha O'Connor, Kate Godfrey, Sara Reed et al.
2 citations
The study aims to uncover the neural mechanisms by which psilocybin-assisted therapy affects obsessive-compulsive disorder (OCD) and whether those brain changes align with improvements in cognitive symptoms. A secondary goal is to test whether a low, tolerable dose is both practical and effective as a clinical treatment. The results will provide essential data for designing a future randomized controlled trial.
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 affect brain microstructure and waste clearance. In 11 CCH patients, subjective sleep quality—measured by the Pittsburgh Sleep Quality Index—improved one week after three doses of psilocybin (0.14 mg/kg) given one week apart, with a mean PSQI change of -2.50 points. Before treatment, CCH patients had poorer sleep and differences in brain microstructure and water diffusivity compared to 24 healthy controls, primarily in grey matter. Psilocybin intervention was not associated with statistically significant changes in brain microstructure or water diffusivity on average, though most patients showed lower white matter diffusivity and neurite volume. Subjective sleep quality showed borderline significant correlations of moderate effect size with brain microstructure and water diffusivity.
Cureus
January 1, 2025
Sorcha O'Connor, Kate Godfrey, Sara Reed et al.
correction
A protocol describes a planned study testing whether a low-moderate dose of psilocybin (10 mg), combined with non-interventional therapy, can improve cognitive flexibility and neuroplasticity in people with obsessive-compulsive disorder (OCD). Twenty blinded participants will receive an active placebo (1 mg psilocybin) in a first session and 10 mg in a second session four weeks later. Cognitive flexibility will be measured with the intradimensional-extradimensional shift task two days after each session, and neuroplasticity will be assessed via electroencephalography immediately after each session. Secondary outcomes include OCD symptom severity and patient-reported measures. The results are expected to clarify neural mechanisms and guide a future randomized controlled trial.
Translational Psychiatry
July 15, 2026
Annette Johansen, Pontus Plavén-sigray, Martin K Madsen et al.
A single dose of psilocybin (0.3 mg/kg) did not produce a statistically significant increase in synaptic density across all fifteen healthy participants. However, those who received psilocybin in a therapeutic-like room reported more intense mystical-type experiences, longer-lasting psychological benefits, and showed greater increases in synaptic density in the frontal cortex and hippocampus compared to those dosed inside an MRI scanner. The findings indicate that environmental context modulates psilocybin's neuroplastic effects, with implications for psychedelic-assisted therapies.