Cannabis and brain activity in young adults 🧠

In young adults prone to psychosis, a reduction in brain connectivity has been observed—a dysfunction that cannabis consumption appears to worsen, according to a new study. This finding could pave the way for treatments targeting psychotic symptoms not addressed by current medications.


In a groundbreaking study, a research team from McGill University found that synaptic density was significantly lower in individuals at risk of psychosis compared to healthy subjects in the control group. A synapse is the space between two neurons that facilitates the transmission of information from one to the other.

"Psychosis doesn't affect all cannabis users, but for some, the risk is high. Our work sheds light on the causes behind this elevated risk," explains Dr. Romina Mizrahi, senior author of the study and professor in the Department of Psychiatry at McGill University.

"It appears that cannabis disrupts the natural mechanism of synaptic strengthening and pruning, which is essential for healthy brain development."

New avenues for treatment development Using advanced brain imaging technology, the team studied 49 individuals aged 16 to 30, some of whom had recently experienced psychotic symptoms or were considered at high risk. Published in *JAMA Psychiatry*, the study's findings indicate that low synaptic density is associated with social withdrawal behavior and lack of motivation—difficult-to-treat issues, according to the scientists.

"The vast majority of current medications target hallucinations but do not address symptoms that complicate social, work, or school interactions," says Belen Blasco, lead author of the study and a PhD candidate in the Integrated Program in Neuroscience at McGill University. "Research on synaptic density could lead to the development of treatments that enhance social skills and improve patients' quality of life."

Cannabis was already known to be a risk factor for psychosis, even schizophrenia, but thanks to this study, a research team has been able to measure real-time structural changes in the brains of individuals at high risk for the first time.

The next step for the research team will be to determine whether the observed changes could help predict the onset of psychotic disorders and potentially intervene before symptoms appear.

The study was conducted at the Douglas Mental Health University Institute and the Montreal Neurological Institute-Hospital of McGill University and was funded by the Canadian Institutes of Health Research.

Reference:
The article "Synaptic Density in Early Stages of Psychosis and Clinical High Risk," by Belen Blasco, Kankana Nisha Aji, Romina Mizrahi et al., was published in *JAMA Psychiatry*.