What does psilocybin actually do inside your head? Over the past 15 years, brain-imaging research in Europe and around the world has started to answer that question. This guide explains what scientists know about psilocybin and the brain, from serotonin receptors and brain networks to neuroplasticity, and what is still uncertain.
This article is for general information only. It is not medical advice.
How Psilocybin Reaches the Brain
After you swallow psilocybin, the body quickly converts it into psilocin. Psilocin then crosses into the brain, where it acts mainly on serotonin 5-HT2A receptors. These receptors are especially common in the cortex, the outer layer of the brain involved in perception, thinking and self-reflection.
In 2019, researchers in Copenhagen used PET scans to measure this directly. Their study in Neuropsychopharmacology found that the more 5-HT2A receptors psilocin occupied, the stronger the psychedelic experience. In other words, the link between psilocybin and the brain starts with this single receptor type.
Psilocybin and the Brain's Default Mode Network
The default mode network is a group of brain regions that are active when we daydream, think about ourselves or replay the past. Some researchers describe it as the brain's "autopilot."
In 2012, a team at Imperial College London published one of the first brain-imaging studies of psilocybin in PNAS. They found reduced activity and connectivity in key hubs of this network. Since then, other studies have confirmed that the network becomes less organized under psilocybin. Many scientists think this may help explain "ego dissolution," the feeling that the usual sense of self fades during a strong experience.
A More Connected Brain
While some networks become less organized, communication between other parts of the brain increases. For example, a 2014 study in the Journal of the Royal Society Interface found many new connections between brain regions that do not usually communicate much. Researchers have suggested that this may explain some of the unusual links between senses, thoughts and emotions that people report.
More recently, a large 2024 study in Nature scanned volunteers many times before, during and after a dose. It found that psilocybin caused a strong "desynchronization" of brain networks, much larger than the effect of a stimulant used as a comparison. Some smaller changes lasted for several weeks.
Psilocybin, the Brain and Depression
These findings have raised hopes for mental health treatment. Depression is often linked to rigid, repetitive thinking, such as constant rumination. Because psilocybin seems to loosen rigid brain patterns, researchers are testing whether it can help people break out of these loops. The same loosening may also play a role in creative thinking, as our article on psilocybin and creativity explains.
In 2022, Imperial College researchers analyzed brain scans from two clinical trials in a study in Nature Medicine. After psilocybin therapy, patients' brain networks became more integrated and less separated. Moreover, those with the largest changes tended to show the biggest improvements in mood. The researchers did not see the same pattern with the antidepressant escitalopram. Even so, these were small studies, and more research is needed. Our guide to psilocybin therapy explains how these trials work.
Psilocybin and Neuroplasticity
Neuroplasticity is the brain's ability to form new connections and adapt. Animal research suggests that psilocybin may boost this process. For instance, a 2021 study in Neuron found that a single dose increased the number of dendritic spines, the small structures that help nerve cells connect, in the frontal cortex of mice. Many of these new spines were still present a month later.
However, results in mice do not automatically apply to people. Scientists are still working out whether similar changes happen in the human brain, and whether they explain any long-term benefits.
Is Psilocybin Harmful to the Brain?
Current evidence does not suggest that psilocybin damages brain cells in the way some other drugs can. It also has low physical toxicity. Nevertheless, it can cause intense psychological effects, and people with a personal or family history of psychosis or bipolar disorder face higher risks. In addition, little is known about the effects of frequent, long-term use, including regular microdosing. Read our guide to microdosing magic mushrooms for more on what is and is not known.
What We Still Don't Know
Research on psilocybin and the brain is moving fast, yet many questions remain. Most imaging studies are small, and brain scans show correlations rather than clear causes. Scientists also debate whether the brain changes, the subjective experience, or both are responsible for any therapeutic effects. Finally, researchers still need larger, longer studies in more diverse groups of people.
Psilocybin and the Brain FAQ
Does psilocybin permanently change the brain?
Some changes in brain connectivity seem to last for weeks after a single dose. However, there is no clear evidence of permanent structural changes in humans.
Why does psilocybin cause visual effects?
Psilocin activates 5-HT2A receptors in the visual cortex and changes how brain regions share information. As a result, the brain processes visual signals differently, which can create patterns, colors and distortions.
Does psilocybin kill brain cells?
There is no good evidence that it does. Its main risks are psychological rather than physical, especially at high doses or in vulnerable people.
Conclusion: Psilocybin and the Brain
Psilocybin works mainly by activating serotonin 5-HT2A receptors. In turn, this loosens the brain's usual network patterns, increases communication between distant regions and may encourage new connections. These findings help explain both the psychedelic experience and the growing interest in psilocybin therapy. Still, the science is young. To understand the basics first, read our guide to what psilocybin is and how it works.
Sources
- Madsen MK, et al. Psychedelic effects of psilocybin correlate with serotonin 2A receptor occupancy and plasma psilocin levels. Neuropsychopharmacology. 2019. doi:10.1038/s41386-019-0324-9
- Carhart-Harris RL, et al. Neural correlates of the psychedelic state as determined by fMRI studies with psilocybin. Proceedings of the National Academy of Sciences. 2012. doi:10.1073/pnas.1119598109
- Petri G, et al. Homological scaffolds of brain functional networks. Journal of the Royal Society Interface. 2014. doi:10.1098/rsif.2014.0873
- Siegel JS, et al. Psilocybin desynchronizes the human brain. Nature. 2024. doi:10.1038/s41586-024-07624-5
- Daws RE, et al. Increased global integration in the brain after psilocybin therapy for depression. Nature Medicine. 2022. doi:10.1038/s41591-022-01744-z
- Shao LX, et al. Psilocybin induces rapid and persistent growth of dendritic spines in frontal cortex in vivo. Neuron. 2021. doi:10.1016/j.neuron.2021.06.008
