Teens: Smoke Pot Now, See IQ Take Hit Later Effect only apparent in those who used frequently before age 18 By Kate Seamons, Newser Staff Posted Aug 27, 2012 3:26 PM CDT 53 comments Comments (©miss.libertine) (Newser) – If you're going to smoke pot frequently, you might want to hold off until you're at least 18. A new study finds that teens who are regular marijuana users may end up with a long-term drop in their IQ—but the trend was only spotted in those who toked often before age 18. The implication, per the AP: Pot takes a bigger toll on the developing brain. The study's findings aren't exactly being reported as ironclad, but experts say the methods used get around criticisms that have dogged some earlier research. In this case, researchers tracked how IQ scores changed between ages 13 and 38 in participants from New Zealand. Stateside, 23% of high schoolers copped to recently smoking pot, according to a government report released in June.