Imagine this: you swallow a single capsule in a carefully controlled clinical setting. Colours intensify, the boundaries between you and the world seem to dissolve and, for a few hours, everything feels deeply interconnected. Then the trip ends. But what if the experience doesn’t? What if it leaves behind lasting changes—not just in how you feel, but in how your brain is wired?
That is the striking finding of a new study by researchers at the University of California, San Francisco, and Imperial College London, published in Nature Communications. The researchers found that a single high dose of psilocybin—the psychedelic compound found in “magic mushrooms”—can leave measurable changes in brain function and possibly even in the brain’s structural connections for at least a month after the psychedelic effects have worn off.
The study involved 28 healthy adults who had never previously taken a psychedelic. In a carefully controlled clinical setting, each participant received two doses on separate occasions: a very low 1mg dose that served as a control and a full 25mg dose.
The researchers examined brain activity, connectivity and structure at three stages—before the drug was administered, during the peak psychedelic experience and one month later. Participants also completed questionnaires about their experiences during the session, as well as assessments of mood, wellbeing and psychological insight over the following weeks.
One of the key findings centred on brain entropy—a measure of how varied and flexible brain activity becomes. Participants who showed a greater increase in entropy after the 25mg dose reported deeper emotional insights the following day. Those who experienced greater insight were also more likely to report improved wellbeing a month later.
The scans also revealed changes. One month after the high dose, different regions of the brain appeared to communicate differently, suggesting that brain networks had become more flexible and reorganised. Researchers also detected changes in white matter pathways linking the prefrontal cortex—the brain region involved in planning, decision-making and self-reflection—to deeper brain structures. These findings suggest that some nerve fibre pathways may have undergone subtle remodelling or become more densely organised, a pattern opposite to that typically seen with ageing and several neurological disorders.
The researchers believe the temporary surge in brain entropy may help the brain escape entrenched patterns of thinking. In effect, the psychedelic state may create a brief window of heightened flexibility, allowing the brain to form new connections before settling into a healthier configuration. Although the study does not establish that psilocybin causes permanent structural changes, it adds to growing evidence that, when used in carefully supervised clinical settings, psychedelic therapy may produce meaningful and lasting psychological benefits by temporarily making the brain more adaptable.
