Just one insightful psychedelic trip can have a profound impact on a person, and a new study goes some way to explaining why.
The research suggests a single dose of psilocybin (the psychedelic compound in 'magic mushrooms') that sufficiently 'shakes up' the brain's tried-and-true patterns could improve a person's mental well-being for up to a month after their trip.
Many studies on the effects of psilocybin have looked at groups receiving the drug for therapeutic reasons.
Instead, this new work investigated how 28 healthy participants who had never tried psilocybin before reacted to a 25 milligram dose, which is enough to elicit a strong psychedelic trip.
The results may help to explain some of the improvements seen in people with depression, addiction, and anxiety.
"We already knew psilocybin could be helpful for treating mental illness," says UC San Francisco (UCSF) neurologist Robin Carhart-Harris. "But now we have a much better understanding of how."
Carhart-Harris and team assessed the novice trippers' experiences through a series of psychological tests to gauge factors like cognitive flexibility, sense of well-being, and psychological insights gleaned during the trip.
To compare these self-reported dimensions with something a bit more objective, the scientists also recorded the brain activity of participants using electroencephalography (EEG), diffusion tensor imaging (DTI), and functional magnetic resonance imaging (fMRI).
EEG readings were taken before the trip, and then one, two, and four and a half hours into it.
Meanwhile, fMRI and DTI readings were taken before the psilocybin session, and then one month after.
Participants undertook two sessions. They were informed that with each session they would receive a dose of psilocybin, but they wouldn't know how much.
In the first session, all participants were given 1 milligram of psilocybin, which is low enough to be considered a placebo. This was the control.
A month later, participants were given 25 milligrams in a second session. The same psychological and neurological tests were conducted in the preliminary phase as during the full-dose replication, to gather baseline data.
As you can imagine, it was obvious to many participants which session had included the drug, which somewhat limits the findings.
Nevertheless, the data revealed a link between a temporary uptick in brain entropy – a measure of how widely the brain's neural activity varies – and psychological insight reported the following day.
Participants with greater brain entropy under the influence of psilocybin, along with next-day psychological insight, also reported greater improvements in psychological well-being one month post-trip.
"Our data shows that such experiences of psychological insight relate to an entropic quality of brain activity and how both are involved in causing subsequent improvements in mental health," explains Carhart-Harris.
"It suggests that the trip – and its correlates in the brain – is a key component of how psychedelic therapy works."
The experience of insight appears particularly crucial to the long-term effects on well-being. Perhaps this could help doctors hone the use of psilocybin in a clinical setting by further investigating what dose and settings promote those deeper revelations.
Some researchers, however, question whether heightened brain entropy is a reliable marker of the psychedelic state. In a recent critical review, for instance, an international team of neuroscientists suggests that this view may oversimplify things. Their review calls for a more nuanced understanding of how entropy relates to the psychedelic experience.
Carhart-Harris and team also acknowledge in their report, "we may not have yet discovered a sufficiently sensitive assay for detecting (true) functional brain changes post-psilocybin," writing that further work will be needed to fill this gap.
Related: Psilocybin Breaks Depressive Cycles by Rewiring The Brain, Study Suggests
But the fact that a single dose of a drug can have lasting effects on subjective well-being – particularly when the trip itself involves physical brain changes that appear related to subjective psychedelic experience and next-day insights – is, as neuroscientist Taylor Lyons from Imperial College London says, "especially exciting."
"Psilocybin seems to loosen up stereotyped patterns of brain activity and give people the ability to revise entrenched patterns of thought," says Lyons.
The research was published in Nature Communications.