New research emerged showing that initiation into marijuana use during adolescence led to increased cortical thinning. The cerebral cortex is the largest part of the brain responsible for many higher-order functions such as sensation, perception, memory, association, thought, and voluntary physical action. Thinning of the cerebral cortex is associated with a number of disease states.
The study, performed across 8 European sites, collected baseline data and imaging from 799 participants over a 5-year follow-up period (56.3% female; mean age 14.4 years). Longitudinal analysis revealed that marijuana use resulted in cortical thinning in a dose-dependent manner. Thus, higher levels of marijuana use resulted in increased cortical thinning. Lifetime marijuana use was not associated with cortical thickness at the beginning of the study or the end of the 5-year follow-up period, suggesting that cortical thinning did not precede initiation of marijuana use and was therefore the result of marijuana use over the follow-up period. At the end of the study period, researchers further noted that thinning of the right prefrontal cortices was associated with increased impulsiveness and diminished attention in study participants.
Drug Free America Foundation epidemiologist Dr. Sharif Mohr commented, “These results are very, very alarming. Cortical thinning is associated with a number of adverse outcomes including depression, Parkinson’s and Alzheimer’s disease. While it’s not entirely clear whether cortical thinning is the cause of these disease states or is merely a marker for them, the fact that marijuana use can precipitate or hasten cortical thinning in young people is a very bad sign.”
Dr. Mohr went on to say, “The research is pretty clear. We know that marijuana legalization means more youth initiating into marijuana use at younger ages; it also means more problematic use of the increasingly potent drug among youth. Lest the cognitive potential of current and future generations be wasted, policymakers, parents, and especially kids need to understand just how detrimental use of high potency marijuana is to the developing brain.”