2024-11-08 15:00:00
08 November 2024
Cannabis use during adolescence is not harmless on the structure of the brain. A Canadian study reveals a thinning of the cerebral cortex. We suspected it, but these researchers were finally able to explain it.
According to a new study led by Graciela Pineyro and Tomas Paus, two researchers at CHU Sainte-Justine in Montreal (Canada), cannabis use during adolescence can lead to thinning of the cerebral cortex. This is the outer layer of the brain, made up of a set of folds (convolutions). The two hemispheres each have four lobes (frontal, parietal, temporal, occipital), which perform specific functions. These encompass cognitive abilities, such as thinking, language, memory, reasoning, and decision-making. The cortex is also involved in sensory perception (such as sight, hearing, touch) and voluntary motor control.
THC directly impacts neurons
The study demonstrates that THC (tetrahydrocannabinol), the main active compound of cannabis, causes a reduction in the arborization of dendrites, this “antenna network” in the extension of neurons, essential for communication between them. Consequence: this phenomenon leads to atrophy of certain regions of the cerebral cortex, a problem at an age when the brain is fully maturing. The researchers reached this conclusion by combining two complementary approaches, one in mice and the other in a group of adolescents.
« Comparing the brain to a computer, neurons would be the central processor, receiving all information through synapses (connections, editor’s note) via the dendritic network », Explains Tomas Paus, professor of psychiatry and neuroscience at the University of Montreal. “ A reduction in the supply of information to the central processor by dendrites makes learning, social interactions and handling new situations more difficult. »
By analyzing magnetic resonance images (MRI) of adolescent brains, these same researchers had already noted that young people who had used cannabis before the age of 16 had a thinner cerebral cortex. But this method could not prove causality or precisely understand the effect of THC on brain cells. This is where the mouse and Graciela Pineyro’s team specializing in molecular biology come in. “This mouse model made it possible to demonstrate that THC modifies the expression of certain genes which influence the structure and function of synapses and dendrites,” she explains. This phenomenon leads to atrophy of the dendritic network, contributing to the thinning observed in certain regions of the cortex.
Source : Navarri X, Robertson DN, Charfi I, et al. Cells and Molecules Underpinning Cannabis-Related Variations in Cortical Thickness during Adolescence. J Neurosci. 2024 Oct 9;44(41):e2256232024
Written by: Hélène Joubert; Edited by Emmanuel Ducreuzet
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**Interview with Dr. Tomas Paus on Cannabis Use and Adolescent Brain Development**
**Interviewer:** Good afternoon, Dr. Paus. Thank you for joining us today. Your recent study highlights some concerning effects of cannabis on the adolescent brain. Can you break down exactly what your research found regarding cannabis use and the cerebral cortex?
**Dr. Paus:** Good afternoon, and thank you for having me. Our study indicates that cannabis use during adolescence is associated with thinning of the cerebral cortex, which is crucial for cognitive functions such as memory, reasoning, and decision-making. We’ve observed that THC, the main psychoactive component in cannabis, negatively affects the dendrites—essentially the ‘antennae’ of neurons—leading to a reduction in their branching and communication capabilities. This is particularly alarming during adolescence when the brain is developing rapidly.
**Interviewer:** That sounds quite significant. What methods did you use to arrive at these conclusions?
**Dr. Paus:** We employed a dual approach, using both animal models, specifically mice, and a cohort of adolescents. By studying the effects of THC in both settings, we were able to draw parallels and gain a better understanding of how cannabis impacts brain structure at a critical maturation stage.
**Interviewer:** You mentioned cognitive functions—how does thinning of the cerebral cortex specifically affect a young person’s day-to-day life?
**Dr. Paus:** Thinning of the cortex can disrupt various cognitive processes. Teens may experience difficulties with thinking, learning, and memory retention. Additionally, it could impair reasoning and decision-making skills, which can have serious consequences, especially during this stage of life where individuals are more vulnerable to risky behaviors, including impaired driving.
**Interviewer:** With the rise of legalized cannabis use, what do you think is the most important takeaway from your research for parents and young adults?
**Dr. Paus:** It’s crucial for them to understand that cannabis is not a benign substance, especially for developing brains. Parents should have open discussions with their children about the potential risks associated with cannabis use. Awareness can empower young adults to make informed choices about their health and wellness.
**Interviewer:** Thank you, Dr. Paus. This information is certainly vital as conversations around cannabis continue to evolve. We appreciate your insights today.
**Dr. Paus:** Thank you for having me. It’s important that we keep this dialogue ongoing to protect our youth’s brain health.
