Study: Marijuana use permanently lowers IQ in teens

Researchers found persistent users of the drug, who started smoking it at school, had lower IQ scores as adults.

They were also significantly more likely to have attention and memory problems in later life, than their peers who abstained.

Furthermore, those who started as teenagers and used it heavily, but quit as adults, did not regain their full mental powers, found academics at King’s College London and Duke University in the US.