Would you give up about 8 IQ points as an adult (or drop from the equivalent of A to B student) in exchange for teenage years spent getting high?
That’s, essentially, the choice we make, according to a new long-term study that followed 1,037 New Zealand children for 25 years.
“The findings are consistent with speculation that cannabis use in adolescence, when the brain is undergoing critical development, may have neurotoxic effects,” study researcher Madeline Meier of Duke University said in a statement, LiveScience reported.
Roughly 5 percent of the participants started using marijuana as teenagers. Those who smoked marijuana at least four times a week and used marijuana throughout their life saw their IQ drop an average of 8 points, the equivalent of going from an A to a B student. The drop was not explained by other drug use, years of education, schizophrenia or using marijuana in the day before the test.
People who eventually quit smoking pot still had lower IQs than they did at the start of the study.
But here’s the real important takeaway from the research: “Interestingly, people who picked up the habit as adults had no IQ drop, suggesting that marijuana may not be as harmful to the mature brain.”
It’s not exactly clear why cannabis harms the teen brain more, but perhaps it’s time to amend the slogan to “Just Say No … ‘Til You’re 25 Or So.”