Marijuana and Teenagers: Does Drug Use Cause a Bad Brain?

January 13, 2011


By Orly Avitzur, MD, MBA

A story in the December 16 issue of Neurology Today®, "Adolescent Marijuana Use May Cause Lasting Cognitive Deficits", raised concerns about teenagers who start smoking before the age of 16. As the mother of two teens, like many parents, I've warned my kids about the dangers of drugs and alcohol since they were young enough to listen. But now that they're old enough to argue (and roll their eyes), they demand more than parental platitudes when I get on my soapbox. This story, based on research presented at this year's annual meeting of the Society for Neurosciences, provides that evidence, and it's quite troubling.

Users who started smoking the drug before age 16 scored consistently lower on tests of cognitive ability and executive function that those who started smoking later in life and healthy individuals who had never used marijuana, researchers found. Moreover, test scores fell proportionally as the amounts of marijuana young subjects used increased. And kids who started smoking before age 16 also smoked more than twice as often per week and nearly three times as many grams of marijuana per week relative to older smokers.

Frances E. Jensen, MD, professor of neurology at Harvard Medical School, and senior associate in neurology at Children's Hospital in Boston, told Neurology Today, "The data from this study are robust and consistent with other studies showing that teens are especially vulnerable because this is a critical stage of development for one of the most sophisticated parts of the brain— the frontal and pre-frontal cortex." He went so far as to urge a public service announcement.

What do you think? Should there be a PSA? Does marijuana cause brain damage? What's the best way to communicate this to teenagers? And if you are the mother of teenagers and one child smokes marijuana for medicinal purposes, like MS, as this Neurology Now® magazine reader recently wrote, does this make things more complicated?

Please send your thoughts to me via e-mail at

For additional information about the risks of marijuana use: