Single psilocybin dose leaves brain changes for a month
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- UCSF and Imperial College London researchers found that a single 25 mg dose of psilocybin produced changes in brain activity detectable a month later, according to a study published in Nature Communications.
- The 28-participant study recruited healthy adults who had never used a psychedelic and used EEG, fMRI, and DTI to compare a 1 mg "placebo" dose with a 25 mg dose in the same volunteers over a multi-week protocol.
- Brain entropy rose within 60 minutes of the high dose, and DTI scans one month later showed neural tracts were denser with greater integrity — a pattern the researchers described as the reverse of changes commonly associated with aging.
- 27 of 28 participants ranked the 25 mg experience as the "single most" unusual state of consciousness they had ever encountered, and reported substantially more psychological insight than after the placebo dose.
- Participants with the largest entropy increases reported more insight the next day, and that insight correlated with stronger improvements in well-being one month later, the researchers concluded.
- Well-being measures improved at two weeks and four weeks after the high dose, and participants performed better on a cognitive flexibility test one month after the experiment.
Why it matters: The study gives researchers a concrete biological mechanism — increased brain entropy and denser neural tracts — to explain why psilocybin therapy appears to help depression, anxiety, and addiction, potentially letting clinicians calibrate doses to maximize therapeutic insight without unnecessary intensity.
