Pot Doesn't Reduce Teen Brain Tissue, Says Study
But regular drinking does. The jury's still out on all this research, however.
Marijuana is less damaging to teenagers' brain tissue than alcohol, according to a new study that scanned the brains of 92 participants—aged 16-20—before and after an 18-month period. Half of the teens, those who already had extensive alcohol or marijuana histories, continued using their drugs of choice in varying amounts over the 18 months; the other half abstained or consumed minimally, as they had throughout their adolescence. The scans indicated that those teenagers who consumed at least five drinks per week showed reduced white matter brain tissue—which develops throughout adolescence and into the 20s—while those who regularly smoked pot did not. According to study co-author Susan Tapert, a neuroscientist at UC San Diego, a reduction in this brain tissue could lead to declines in memory, attention and decision-making in later adolescence and adulthood. "It becomes a cycle. If teens decrease their tissue health and cognitive ability to inhibit themselves, they might become more likely to engage in risky behavior like excessive substance use," explains co-author Joanna Jacobus, a postdoctoral fellow at UC San Diego. However, both Tapert and Jacobus say they're not sure why marijuana didn't have an effect while alcohol did—and both agree that more definitive research needs to be conducted to confirm their findings. The study also contradicts the findings of research from Duke University earlier this year, which found that long-term pot use could lead to a significant IQ drop. And it's pretty imperative we find out for sure—according to a yet another study from the University of Michigan earlier this week, 23% of polled high school seniors had smoked pot within the last month.