Study Finds Brain Structural Changes Persist One Month After Single Psilocybin Dose in Healthy Volunteers

A single 25mg dose of psilocybin, the active compound in magic mushrooms, triggered anatomical changes in the brains of healthy volunteers that persisted for at least one month, according to a new study. The research, conducted on 28 individuals who had never taken psychedelics before, revealed a surge in brain entropy within an hour of ingestion, suggesting the brain processed a greater diversity of information.

Those with the largest entropy spikes were most likely to report deeper psychological insight and better wellbeing weeks later.

The study began with participants receiving a 1mg placebo dose of psilocybin. Scientists then used electroencephalography (EEG) with electrodes on the scalp to measure brain activity, alongside functional MRI scans and diffusion tensor imaging (DTI) to monitor brain structure.

Over the following weeks, volunteers completed tests assessing wellbeing, depth of psychological insight, and flexibility of thinking.

One month after the placebo, the same participants took the full 25mg dose, which elicited a powerful psychedelic experience. During and after this experience, researchers repeated the EEG, functional MRI, DTI scans, and psychological tests. Within an hour, EEG showed the surge in brain entropy, indicating more varied neural activity.

DTI scans one month later detected a drop in diffusion along nerve tracts from the front to the middle of the brain. This drop could result from pruning of some nerve fibers or the growth of new nerves not yet covered with insulating sheaths. The changes aligned with positive outcomes, as participants who experienced the biggest entropy increases reported the most significant improvements in mental flexibility and overall wellbeing.

The study explored the entropic brain effect, where psychedelics make neural activity more varied. It was led by Prof Robin Carhart-Harris and colleagues at Imperial College London, with findings published in Nature Communications. The research was a cross-over study, assessing volunteers after both the 1mg placebo and the 25mg dose.

Prof Alex Kwan, a neuroscientist at Cornell University in New York, noted that studies in mice have shown psychedelics can rewire nerve connections. However, he pointed out the study involved a small number of people and that DTI provides an indirect and limited view of brain connections.

According to @EricTopol, a single 25mg dose of psilocybin leads to brain structural changes seen at one month, based on the cross-over study of 28 healthy volunteers with no prior psychedelic experience who were also assessed after 1mg.

The findings build on evidence that psychedelics may boost flexible thinking and help escape destructive cognitive patterns, potentially explaining therapeutic effects on anxiety, depression, and addiction. While preliminary, the observed changes contrast with those seen in aging and dementia, where nerve tracts often become less dense.