Journal of Psychopharmacology
December 17, 2021
Josephine Marschall, George Fejer, Pascal Lempe et al.
69 citations
In a double-blind, placebo-controlled, within-subject crossover study, psilocybin microdosing (a sub-hallucinogenic dose taken every third day) did not alter emotion processing, symptoms of anxiety or depression, or self-reported interoceptive awareness compared with placebo. Exploratory analyses showed that symptoms of depression and stress were significantly reduced in the first block compared with baseline, but participants broke blind in the second block, and there was no effect of expectations. The authors call for further research in a substance-naïve population with clinical-range anxiety and depressive symptoms to substantiate potential beneficial effects.
Psychopharmacology
April 30, 2021
Michiel van Elk, George Fejer, Pascal Lempe et al.
53 citations
People who take small, non-hallucinogenic doses of psilocybin (microdosing) report feeling more awe when watching videos of funny animals and moving objects compared to when they take a placebo. However, about two-thirds of participants correctly guessed whether they had received psilocybin or placebo, suggesting that expectancy effects—rather than the drug itself—may explain the subjective benefits of microdosing. The study used a double-blind, placebo-controlled crossover design with a microdosing workshop and lab visits over several weeks.
Current Psychology
September 8, 2023
Camile Bahi, Mona Irrmischer, Katrien Franken et al.
27 citations
A single session of connected breathing reduced negative mood states (anger, tension, confusion, depression) and increased esteem in 20 healthy adults aged 23–39. Electroencephalography recordings showed decreased delta and theta brainwave power in frontotemporal and parietal regions, and decreased beta1 and beta2 power in parietotemporal regions. Experienced practitioners showed increased gamma power. Subjective experiences during breathwork resembled those after medium to high doses of psilocybin, indicating mystical-type experiences. The results suggest breathwork alters brain activity and mood and may improve mental well-being.
June 14, 2021
Luisa Prochazkova, Michiel van Elk, Josephine Marschall et al.
4 citations
preprint
Microdosing psychedelic truffles increased the quality of divergent thinking, measured as the ratio of original responses to total responses on the Alternative Uses Task, in a pooled analysis of three double-blind placebo-controlled trials with 175 participants. The unadjusted originality score was significantly higher only when relative dosage (dose per body weight) was considered. No effects were found on convergent thinking or other divergent-thinking scores. The effects were subtle and persisted after controlling for expectation and demographic biases. The findings underscore the importance of controlling for placebo effects and prior psychedelic experience in microdosing research.
Neuropharmacology
November 2, 2025
Luisa Prochazkova, Josephine Marschall, Michiel van Elk et al.
2 citations
Microdosing psilocybin from truffles modestly improved the quality of divergent thinking—specifically the ratio of original responses to total responses—in a pooled analysis of three double-blind, placebo-controlled trials with 171 participants. The effect on unadjusted originality was significant only when dosage relative to body weight was considered, and it remained after controlling for dose guess and demographic biases. No effects were found on other measures of divergent thinking or on convergent thinking. The findings underscore the need to account for placebo effects and prior psychedelic experience when evaluating microdosing claims.
May 2, 2024
Jeremy I Skipper, George Fejer, Matthieu Koroma et al.
preprint
Language plays a generative role in shaping and sustaining consciousness, not merely reporting it. Cognitive neuroscientist Jeremy I. Skipper argues against localizationist models of language processing, emphasizing context-dependent and dynamic brain recruitment. Aphasic patients report loss of self-narrative and increased connectedness, paralleling psychedelic states where linguistic categories dissolve and ineffability arises. Potential neural mechanisms linking language disruption to psychedelic experiences are outlined. The UNITy Project aims to study post-acute meaning-making processes and predict changes in language and well-being after psychedelic sessions.
George Fejer, Manoj Doss
preprint
Manoj Doss critiques five methodological sins in psychedelic research, focusing on biases from researchers' personal drug experiences and self-experimentation. He argues for integrating cognitive psychology with neuropharmacology and using empirical, behavioral measures to study psychedelics' effects on cognition and memory, aiming to advance a more rigorous scientific understanding of these substances.