Do your stoner friend's theories about government spies and Doritos sound stupid? That's because they probably are stupid. A new study has found that teenagers who smoke pot before they turn 18 are at risk for a lower IQ.
The study, published in the Proceedings of the National Academy of Sciences, took a massive, careful look at teen pot usage. It followed 1,000 people in New Zealand over a 20-year-period, HealthDay reported. The researchers found that participants who started smoking at least once a week before turning 18 and who continued to smoke as adults suffered an average IQ drop of 8 points.
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And the damage was permanent. Adults who stopped smoking marijuana as they grew older failed to gain back the IQ points they lost. The researchers wrote that marijuana can be toxic for young brains.
However, there is some good news: it's just the developing brains that marijuana seems to harm. "I'm fairly confident that cannabis is safe for over-18 brains, but risky for under-18 brains," a member of the research team told BBC News.