Cannabis use is prevalent among teens, whose brains are undergoing massive developmental changes. Evidence suggests that THC (tetrahydrocannabinol), the primary psychoactive ingredient in cannabis, has profound effects on the brain, impairing neurodevelopment. A recent study in mice found that adolescent cannabis use influences gene expression and neural connections, potentially altering the brain’s structure.

Researchers exposed adolescent male mice to THC and then analyzed changes in gene expression and brain cell structure within the cerebral cortex—a brain region responsible for memory, thinking, learning, reasoning, problem-solving, emotions, consciousness, and sensory functions. They also scanned the brains of more than 450 adolescent human males to compare the cerebral cortex thickness of those who tried cannabis before age 16 to those who did not.

They found that adolescent mice exposed to THC exhibited less dendritic branching and fewer neural spines, indicating a loss of complexity in brain cells. Similarly, human teens who used cannabis had thinner cortex regions. Further analysis linked these structural changes to genes involved in brain development, including processes like learning and memory.

These findings suggest that early cannabis exposure interferes with the normal development of brain structure, especially in areas critical for learning and emotional regulation. This interference likely occurs through effects on specific genes and brain cells responsible for building neural connections during adolescence.

Teens aren’t the only ones at risk for the harmful developmental effects of THC exposure—the compound can pass into breast milk, influencing an infant’s neurodevelopment. Learn more in this clip featuring Dr. Rhonda Patrick.