Single Psilocybin Dose Reshapes Brain Function and Anatomy

A single, high dose of psilocybin can trigger functional and anatomical brain changes detectable from one hour to one month after administration.

In a 2026 placebo-controlled study of 28 healthy psychedelic-naive participants, researchers used EEGs and fMRIs to measure these changes after a 25 mg dose.

Within one hour, EEG showed a surge in brain entropy, indicating the brain was processing more diverse information and accessing a wider range of mental states. Diffusion tensor imaging one month later revealed thinning of white matter fibers across the prefrontal cortex and subcortical regions.

Researchers reported increases in cognitive flexibility, psychological insight, and wellbeing at the one-month mark. All but one participant rated their experience as the single most unusual conscious state of their lives; the remaining participant placed it in their top five.

The findings suggest psychological insight mediates the link between the entropic brain effect and enduring wellbeing improvements.