By NICK CHILES
We all remember the stoners, druggies, pot heads from high school—those dudes who sat in the back of the classroom, their clothes already reeking at 10 a.m. with the stench of the weed smoke that had just enveloped them out in the park, or behind the school, or (if your school was particularly bad) in the boys bathroom. They always seemed a little out of it, a little slow on the draw, surely headed for a life of not-much-of-anything.
Hell, forget about remembering them—maybe some of you were one of them?
Turns out that those stoners actually were doing irreparable harm to their brains. As we’ve been hearing for years, weed does kill brain cells if you start smoking it as a teenager.
A study of more than 1,000 people in New Zealand who were followed over two decades found that those who started habitually smoking marijuana before age 18 eventually showed an 8-point drop in IQ.
If you’re thinking that 8 points ain’t that bad—maybe worth giving up in exchange for all those years of a sweet, mind-dulling high—you should know this: Because the average IQ is 100 points, a drop of just eight points in IQ would mean falling from the 50th percentile to the 29th percentile in terms of intelligence. In other words, a drop from average to near-moron. (And since we’re talking averages, that means many of the subjects likely dropped a lot more than 8 points.)
The study, published yesterday in the Proceedings of the National Academy of Sciences, should be printed out and laminated by all those parents who are about to have that crucial anti-drug talk with their kids. If you’d rather use the more subtle approach, start slipping these facts into casual conversation around the family dinner table: Oh, you want me to get you some more juice? Did you know that pot will make you stupid?
Now all of you grown-ups out there who have become habitual pot smokers a little later in life—you know who you are!—and wondering if you have been zapping brain cells, you can rest a bit easier: Those who didn’t start smoking until after adolescence showed no adverse effects on intelligence. (But even knowing that, you still can’t remember where you put those keys, huh?)
The researchers started with a baseline intelligence for all study subjects, testing them when they were under 13 and hadn’t yet started smoking and then assessing them at five different “waves”—ages 18, 21, 26, 32, and 38. The researchers assessed marijuana use and tested intelligence. The authors also controlled for alcohol use, other drug use and education level.
According to the study, the eight-point drop was found in subjects who started smoking in adolescence and persisted in “habitual smoking”—using it at least four days per week—in three or more of the five testing waves. People who started smoking in adolescence but used marijuana less persistently still had a hit to their IQ’s, but it was less pronounced than the group that used it early and persistently.
Those who never used marijuana actually got smarter by nearly one IQ point on average.
Madeline Meier, lead researcher and a post-doctoral associate at Duke University, said that persistent use of marijuana in adolescence appeared to blunt intelligence, attention and memory. More persistent marijuana use was associated with greater cognitive decline.
“Collectively, these findings are consistent with speculation that cannabis use in adolescence, when the brain is undergoing critical development, may have neurotoxic effects,” Meier writes in the study.
Alarmingly, subjects who stopped using marijuana for a year still showed the persistence of adverse effects and some neurological deficits. But those who didn’t start smoking until after adolescence showed no adverse effects on intelligence.
Scientists believe they isolated the reason why this early use is so harmful. It has to do with a substance called myelin—which is a kind of insulation for nerve cells in the brain that also helps speed brain signals along. But in adolescent brains, the protective coating it forms is not yet complete.
We need to reach our kids as early as possible with this information because, according to statistics released in June by the U.S. Centers for Disease Control and Prevention, American teenagers today are more likely to be smoking marijuana than cigarettes. That’s because they think weed is less harmful than cigarettes. Now we know that’s not true.
So we must spread the word, as far and wide as possible: The next hit you take could mean a permanent spot working the fries at McDonald’s.
Mom. NY Times bestselling author. Pop culture ninja. Unapologetic lover of shoes, bacon and babies. Nice with the verbs. Founder of the top black parenting website, MyBrownBaby.