A single dose of psilocybin, a psychedelic drug that's being fast-tracked for U.S. approval, causes anatomical brain changes that last for up to a month, according to a study that provides never-before-seen insight into how such drugs affect the mind.
Twenty-eight healthy volunteers who had never taken a psychedelic drug were given either a single 25-milligram dose of a psilocybin pill developed by Compass Pathways or a placebo and monitored with brain imaging and measurement techniques before, during and one month after the treatment, researchers reported in Nature Communications.
Psilocybin led to increased entropy - the diversity of neural activity in the brain - in the minutes and hours after taking the drug, suggesting the psychedelic led the brain to process a richer body of information, the researchers said.
The degree of entropy predicted how much insight, or emotional self-awareness, participants felt the next day. This in turn predicted improvements in their sense of well-being a month later.
“Psilocybin seems to loosen up stereotyped patterns of brain activity and give people the ability to revise entrenched patterns of thought,” study leader Taylor Lyons of Imperial College London said in a statement.
The U.S. Food and Drug Administration recently gave a “priority voucher” to Compass, which is testing its drug in patients with treatment-resistant depression, significantly cutting the agency’s review time for potential approval.
In previous late-stage trials, single doses of psilocybin have reduced symptoms within days in patients whose depression had not responded to traditional therapies.
In the new study, one month after the psilocybin dose, an MRI test that measures diffusion of water along neural tracts in the brain found less diffusion than before the treatment - the opposite of what happens in aging, when white matter loses integrity and diffusion increases, according to the report.
Volunteers who experienced the largest increases in brain entropy in the hours after taking psilocybin were the most likely to have increased insight the next day and increased well-being a month later, leading the researchers to conclude that improved well-being was driven by the experience of insight.
The findings could improve treatment for people with mental illness, the researchers said.
“We already knew psilocybin could be helpful for treating mental illness,” senior researcher Robin Carhart-Harris of UCSF said in a statement. “But now we have a much better understanding of how.”
