Psychedelic compounds such as psilocybin, LSD, mescaline, DMT, and ayahuasca each have their own unique chemical structures. These compounds have been used throughout history across different periods and cultural contexts. Until now, most research has focused on these substances in isolation, making it difficult to see the bigger picture of how they affect the brain. However, a new large-scale study now suggests that these five psychedelics may share a common effect on brain activity.
The largest brain imaging analysis of psychedelics to date, recently published in Nature Medicine, has identified two patterns of brain activity that appear across all five drugs. This discovery could influence how scientists develop new treatments for mental health conditions.
Pooling a Decade of Data
Research on psychedelics has often been limited by practical challenges. High costs, strict regulations, and ethical concerns usually restrict studies to small groups of participants, often no more than 10 to 30 people. As a result, it has been very difficult to compare the effects of different psychedelics within a single experiment.
To address these limitations, an international team led by Danilo Bzdok at McGill University brought together brain imaging data from 11 studies conducted across five countries. The researchers pooled over 500 brain scans from 267 participants to create the most comprehensive picture yet of how psychedelics affect the brain. “This approach gives us an X-ray view of the entire research community,” said Bzdok, Associate Professor in McGill’s Department of Biomedical Engineering.
Two Consistent Changes
The researchers found that, despite their chemical differences, all five psychedelics produced two consistent changes in brain activity. The first change affects the brain’s internal networks. In a typical state, each network communicates within itself, keeping its activity organized and separate from other networks. Under the influence of psychedelics, these internal connections become weaker, and the networks lose some of their usual structure.
The second change is the opposite. As the internal connections weaken, communication between different brain networks increases. Signals begin to cross between networks that are usually separate. The researchers suggest that this increased cross-talk may help explain why people experience hallucinations, changes in perception, and unusual thoughts when using psychedelics.
The analysis also identified an increased connection between higher-level brain networks, such as those involved in thinking, emotion, and decision-making, and the sensory networks that control vision and movement. Important regions deep in the brain, like the thalamus, also showed changes in activity. “This is a breakthrough in how we think about psychedelic drugs,” said Bzdok. “For the first time, we show there’s a common denominator among drugs that we currently consider completely separate.”
Emerging From the Research Winter
These results come at a time when scientific interest in psychedelics is growing again. Since the 1970s, research in this area has slowed down because of legal restrictions and the association of psychedelics with counterculture movements. Scientists often refer to this period as the “psychedelic research winter.”
In recent years, new brain imaging tools and expanded clinical studies have helped end this research drought. These advances suggest that psychedelics could provide benefits for conditions such as depression, PTSD, and addiction, especially where current treatments have made little progress. “Many drug therapies for depression, for example, have changed little over the past decades,” Bzdok said. “Psychedelics may represent the most promising shift in mental health treatment since the 1980s.”
A Benchmark for What Comes Next
In addition to its main findings, the study aims to provide a reference for future research. The field of psychedelic neuroscience is still navigating the practical and regulatory hurdles that have historically limited its scope, and individual studies have sometimes produced inconsistent or conflicting results.
This analysis offers a starting point for future studies by mapping a shared pattern of brain activity across five different drugs and several research centers. The authors believe that these results could also support efforts to ease some of the strict regulations that have limited research in this field.
The question of why these chemically distinct compounds produce the same two changes in the brain remains open. However, recognizing that they do is an important step toward understanding how psychedelics work and how this knowledge might be used to improve clinical mental health treatments.
Austin Burgess is a writer and researcher with a background in sales, marketing, and data analytics. He holds an MBA, a Bachelor of Science in Business Administration, and a data analytics certification. His work focuses on breaking scientific developments, with an emphasis on emerging biology, cognitive neuroscience, and archaeological discoveries.