Study Reveals Lasting Structural Brain Changes

Scientists observed apparent changes in brain structure that remained visible a month after healthy volunteers took the psychedelic compound, according to research published in Nature Communications. The findings suggest a potential link between psilocybin use and therapeutic effects for conditions like anxiety, depression, and addiction.

Insights From Advanced Brain Scanning

Specialised scans that measured the diffusion of water along nerve bundles in the brain revealed that some nerve tracts had become denser and more strong after the drug was taken. This pattern contrasts with what is typically observed in conditions such as ageing and dementia, where nerve structures tend to degrade over time.

“It’s remarkable to see potential anatomical brain changes one month after a single dose of any drug,” said Prof Robin Carhart-Harris, a neurologist at the University of California, San Francisco, and senior author on the study. “We don’t yet know what these changes mean, but we do note that overall, people showed positive psychological changes in this study, including improved wellbeing and mental flexibility.”

Researchers have long sought to understand how psychedelics affect the brain, with renewed interest following studies indicating their potential to treat various mental health disorders, while the compounds are thought to help by promoting flexible thinking and enabling individuals to move past unproductive cognitive patterns.

In the latest study, Carhart-Harris and colleagues from Imperial College London investigated the “entropic brain effect,” where neural activity becomes more varied on psychedelics, as well as the drug’s impact on participants’ wellbeing and any corresponding functional or anatomical brain changes.

The study began with 28 healthy volunteers who had never taken a psychedelic; Participants first received a 1mg dose of psilocybin, considered a placebo; the researchers used electroencephalography (EEG) to monitor brain activity through electrodes placed on the scalp.

Over the following weeks, volunteers completed a series of tests to assess their wellbeing, depth of psychological insight, and cognitive flexibility — Functional MRI scans and diffusion tensor imaging (DTI) were also used to monitor brain activity and structure.

A month later, participants took a 25mg dose of psilocybin, sufficient to produce a powerful psychedelic experience; the same tests and monitoring were repeated during and after the session to track changes.

Within an hour of taking the 25mg dose, EEG measurements revealed a significant increase in brain entropy, suggesting the brain was processing a greater variety of information. A month later. DTI scans showed a reduction in diffusion along nerve tracts connecting the front and middle of the brain. This could indicate either the pruning of some nerve fibres or the growth of newly developed nerves without insulating sheaths, though further research is needed to confirm the exact mechanism.

Psychological Benefits and Future Implications

The researchers noted that participants who experienced the largest increase in brain entropy after taking psilocybin were most likely to report deeper psychological insights and improved wellbeing a month later. This correlation highlights the connection between flexible thinking and enhanced mental health.

“It suggests a psychobiological therapeutic action for psilocybin,” said Carhart-Harris, while this finding could help explain why some individuals experience therapeutic benefits from the drug, such as relief from anxiety and depression.

Prof Alex Kwan. A neuroscientist at Cornell University in New York, commented that studies in mice have shown psychedelics can rewire nerve connections, a process known as “plasticity” that may underlie their therapeutic effects. The challenge has been determining whether this also occurs in humans.

“This study comes closer than most to addressing that question, by providing evidence of lasting changes in brain structure after psychedelic use,” he said. However, Kwan also noted the study’s limitations, including its small sample size and the fact that DTI offers an indirect and limited view of brain connections. While the results were “exciting,” further research is needed to confirm and expand on these findings.