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Cannabis use may lead to thinning of the cerebral cortex in adolescents, research in mice and humans suggested.

The multilevel study demonstrated that tetrahydrocannabinol (THC), an active substance in cannabis, causes shrinkage of dendritic arborization — the neurons’ network of antennae that play a critical role in communication between brain cells.

The connection between dendritic arborization and cortical thickness was hinted at in an earlier study by Tomáš Paus, MD, PhD, professor of psychiatry and addictology at the University of Montreal, Montreal, Quebec, Canada, and colleagues, who found that cannabis use in early adolescence was associated with lower cortical thickness in boys with a high genetic risk for schizophrenia. Tomáš Paus, MD, PhD “We speculated at that time that the differences in cortical thickness might be related to differences in dendritic arborization, and our current study confirmed it,” Paus told Medscape Medical News .

That confirmation came in the mouse part of the study, when coauthor Graciela Piñeyro, MD, PhD, also of the University of Montreal, counted the dendritic branches of mice exposed to THC and compared the total with the number of dendritic branches in unexposed mice. “What surprised me was finding that THC in the mice was targeting the same type of cells and structures that Dr Paus had predicted would be affected from the human studies,” she told Medscape Medical News . “Structurally, they were mostly the neurons that contribute to synapses in the cortex, and their branching was reduced.” photo of Pineyro Graciela Paus explained that in humans, a decrease in input from the affected dendrites “makes it harder for the brain to learn new things, interact with people, cope with new situations, et cetera. In other words, it makes the brain more vulnerable to everything that can happen in a young person’s life.”

The study was published online on October 9 in the Journal of Neuroscience . Of Mice, Men, and Cannabis

Although associations between cannabis use by teenagers and variations in brain maturation have been well studied, the cellular and molecular underpinnings of these associations were unclear, according to the authors.

To investigate further, they conducted […]

Cannabis Use Linked to Brain Thinning in Adolescents