Translated from our German original by AI. The German text was researched, written, and edited by the Psychedelia Foundation team and remains the authoritative version.
A single dose of the psychoactive mushroom compound psilocybin could be associated with measurable changes in brain activity, brain scans, and subjective experience weeks later, beyond the acute psychedelic effects. That is suggested by an exploratory study with 28 healthy adults who had no previous experience with psychedelics.
In the placebo-controlled study, all participants first received a very low control dose of 1 milligram of psilocybin. Four weeks later, the same people were given a high dose of 25 milligrams. The researchers recorded changes using EEG measurements and various MRI techniques, both during the acute effects and up to one month after intake.
One to two hours after the 25 milligram dose, the EEG showed clearly altered patterns of activity in the brain. The stronger these changes were during the acute effects, the better a later improvement in mental wellbeing could be predicted. According to the researchers, part of this relationship was linked to personal insights that participants reported on the day after the session.
One month after the high dose, certain MRI measurements showed altered values in the nerve connections between the frontal lobe and deeper brain regions. Such measurements can point to changes in the microstructure of nerve pathways, but on their own they say nothing about which biological processes lie behind them.
The research team also observed changes in the functional organization of brain networks. Participants in whom these values decreased more strongly reported, on average, a greater increase in their subjective wellbeing after one month.
In addition, four weeks after the high-dose session, participants reported more mental flexibility, stronger personal insights, and greater wellbeing.
Lasting changes in general functional brain activity, however, could barely be demonstrated overall. All of the observed effects occurred only after the 25 milligram dose; the low control dose produced no comparable changes.
The authors stress the exploratory character of the study and the small number of participants. The results therefore provide no conclusive evidence of long-term biological remodeling in the brain, but they do show that even a first psilocybin experience can still be associated with measurable changes in psychological and neurobiological measures weeks later.
