The human brain is not fully developed until about age 25, which makes the developing brain vulnerable to anything that can impact neural networks — including regular cannabis use (defined as weekly or more frequent cannabis use over a period of months to years).
Research has shown that THC affects the same system that directs brain development. While a mature brain has already gone through the process of pruning neurons in order to optimize itself for adulthood, this essential process continues throughout adolescence until around the age of 25. The prefrontal cortex — which contributes to functions such as attention, planning and self-regulation — is one of the areas that undergoes the most fine-tuning. It is also the region of the brain most susceptible to the effects of cannabis use before the brain is fully developed.
Neuroimaging has been used to observe how cannabis use affects the brain. Studies using structural MRIs, which look at the brain’s anatomy, suggest that cannabis use may physically alter white and grey matter (critical components of the central nervous system), especially among people who began using cannabis in their early teens. Results from functional MRIs, which measure changes in blood flow to active areas of the brain, have revealed altered blood flow in people who consume cannabis, which may negatively impact cognitive function.
It’s important to remember that most adolescents will not consume cannabis, while some will consume cannabis recreationally without their use becoming problematic. A small subset of adolescents who consume cannabis may develop problems as a result of their consumption.