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Study: Marijuana could be making teens less intelligent

A study found teenagers who use marijuana at least four days a week lost 8 IQ points between the ages of 13 and 38.
Credit: KHOU
A study found teenagers who use marijuana at least four days a week lost 8 IQ points between the ages of 13 and 38.

HOUSTON — In Texas, marijuana is illegal, and a Duke University study says using it can make you less smart.

For decades, researchers studied more than 1,000 people in New Zealand. They found teenagers who use marijuana at least four days a week lost 8 IQ points between the ages of 13 and 38.

Here's the key: that same thing didn't happen for people who heavily smoked marijuana only as adults. Heavy pot smokers did show deficits in memory, concentration and just overall brainpower. But all those effects were much worse among those who started lighting up as teens.

So is an 8-point IQ loss significant? Researchers say you bet. A person's long-term job prospects, job performance an income could be impacted, too.

Researchers can't say for certain marijuana is the sole reason those IQs took a hit. A competing study found a person's socioeconomic status could also be to blame for the IQ slide.

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