Regular marijuana use during the teen years can have lasting effects on the brain.
That's according to Duke University Researchers who followed more than 1,000 pot smokers during adolescence and into adulthood.
Those who began using marijuana before the age of 18 averaged an eight point drop in IQ score by the age of 38. And quitting pot did not reverse this loss.
Researchers say teens' brains are still being formed, and more vulnerable to the effects of drugs.
Study subjects who started using marijuana in adulthood did not show similar cognitive declines.