A SINGLE, high dose of psilocybin, commonly known as magic mushrooms, can trigger functional and anatomical brain changes that can be detected one hour to one month after administration.
Psilocybin 25 mg
In an exploratory, placebo-controlled 2026 study of 28 healthy participants, who had never taken psychedelic substances before, researchers used EEGs and functional MRIs (fMRIs) to measure anatomical and functional brain changes from one hour to one month after a single, 25 mg dose of psilocybin.
Participants first took a 1 mg dose, small enough to be considered a placebo, of psilocybin.
A month later, they took the 25 mg dose, ingesting enough to trigger a powerful psychedelic experience.
Boosting Brain Entropy
Within one hour, researchers saw a surge in brain entropy through EEG, suggesting the brain was processing a greater diversity of information and exhibiting a wider repertoire of potential mental states.
Again within just hours after dosing, researchers were able to predict improved psychological wellbeing of the participants at the one-month stage.
Carried out before and one month after dosing, diffusion tensor imaging revealed a thinning of white brain matter fibres across the prefrontal cortex and subcortical regions.
Also one month after taking the psilocybin, increases in cognitive flexibility, psychological insight, and wellbeing were seen in participants, researchers reported.
Whilst enduring functional brain changes were largely absent, researchers said they are less robust and reliable in healthy populations compared with people who are mentally unwell.
All but one participant who took the 25 mg dose of psilocybin rated their psychedelic experience as the “single most unusual conscious state of their entire lives”.
The remaining participant ranked it within their “top five most unusual conscious experiences”.
Findings suggest that psychological insight plays a role in mediating the causal association between the entropic brain effect and potentially enduring improvements in wellbeing, authors concluded.
Reference
Lyons T et al. Human brain changes after first psilocybin use. Nat Commun. 2026;DOI:10.1038/s41467-026-71962-3.
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