Marijuana Use Impedes Development in Young Brains

A series of studies indicate that teenagers who use marijuana are doing more than just flirting with a gateway drug: They’re probably doing lasting damage to their still-developing brains. A review from the University of Wisconsin, which examines data from studies on both teenage binge drinking and marijuana use, found that adolescents who use cannabis regularly earn lower grades, perform more poorly on IQ tests, and demonstrate lower cognitive function than peers who abstain.

Many short-term problems are associated with substance abuse in young people. Teenagers get less sleep, and sleep more poorly, when they are intoxicated, and being poorly rested may cause them to be less attentive in class and to operate with lower processing speed and working memory. Being under the influence of substances is also associated with poorer emotional regulation and risky decision-making.

But the UW review found that marijuana use presents more lasting dangers as well. Teenage brains exposed to marijuana may fail to develop properly. The damage was found to be particularly severe for teenagers who started younger or who used marijuana frequently. One longitudinal study revealed that young people who smoked marijuana on a regular basis during their teenage years lost an average of 8 IQ points as they transitioned from childhood to adulthood.

The teenage years are critical for brain development, and it seems that toxins in marijuana prevent the brain from doing the important work of pruning extraneous synapses and therefore working more efficiently.

It's important to keep in mind that the marijuana used by teens today differs from that which parents may have used in college. As noted by the University of Washington Alcohol and Drug Abuse Institute, the potency of marijuana today is two to seven times what it was in the 1970's, as measured by the levels of THC, the active ingredient responsible for marijuana's psychoactive, or mood altering, effects. In addition, "another difference between then and now is that marijuana users in the 1970's were most likely to smoke the leaves and initiate use around 20 years of age. Marijuana users today, however, start in their mid-teens and prefer to smoke the more potent flowering tops, (buds) of the plant." Parents need to be mindful of these facts as they speak to their teens about the long term impact of early marijuana use. 

Illustration: National Institute on Drug Abuse