How Psychedelics Change the Brain
Psychedelics like LSD and psilocybin show promise for treating mental health issues such as PTSD and depression. However, scientists haven't fully understood how these substances affect the brain.
A new study looked at over 500 brain scans from 267 people worldwide. It found a "signature" pattern of brain activity caused by different psychedelics. The research, published in Nature Medicine, suggests these compounds boost connections between brain networks. This includes networks for thinking and those for vision and touch.
Manesh Girn, a neuroscientist and study co-author, explained that the brain usually keeps external perception separate from memory and abstract thought. Psychedelics might close this gap between how we think and how we perceive the world.
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Many studies have used MRI scans to examine brains on psychedelics. But these studies often had few participants and inconsistent results. This is partly because psychedelic research is still new. Also, scientists use different ways to measure brain activity.
To fix this, researchers spent five years gathering 11 fMRI datasets from five countries. They studied four psychedelics: psilocybin, LSD, mescaline (from the peyote cactus), and DMT (including in ayahuasca). Processing all the data the same way showed that these psychoactive compounds have similar effects.
Danilo Bzdok, another study co-author, noted that despite differences in how these drugs work chemically, they all affect the human brain in a common way. This finding was surprising and challenges how we categorize these substances.
The study also challenges earlier ideas that psychedelics break down brain networks. Instead, the team found that the drugs seem to strengthen certain connections. For example, areas involved in advanced thinking were much more connected in people who took the drugs compared to sober individuals.
Amy Kuceyeski, a neuroscientist not involved in the study, called the work a "tour de force." However, she would have liked to see how age and sex might influence the effects.
Breaking Down Rigid Thoughts
Christopher Pittenger, a psychiatrist at Yale University, suggested that this increased integration of information across brain regions might explain how psychedelic therapy works. It could break down rigid thought patterns and increase mental flexibility. This is thought to help patients with depression and addiction.
As psychedelic research continues, the team hopes scientists will map the full range of experiences people report. This study looked at brain scans from people minutes into their trips. However, a psychedelic trip can last for hours.
Girn noted that trips can involve many different experiences, from intense visuals to "ego death," remembering memories, or processing emotions. Future studies could explore how these different experiences look in the brain and how they relate to therapy outcomes.
Deep Dive & References
A common neural signature of the psychedelic state in the human brain - Nature Medicine, 2026
