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PORTLAND -- Marijuana is becoming more culturally acceptable than ever, but some researchers worry that with wider acceptance will lead to more teens using the drug.

Oregon Health & Sciences University researcher Bonnie Nagel has seen actual changes in the brains of teens who smoke pot.

We see some compromise in those brain areas. So the front part of the brain, the frontal lobes, abnormalities in the tissue in that part of the brain as well as in the posterior region of the brain as well, said Nagel.

The researcher said those are areas that control focus, decision making, problem solving, planning and other important tasks. Nagel said smoking pot puts bad chemicals into the growing brain.

Because it s so actively developing during those teenage years -- its particularly vulnerable to all of these different types of neurotoxic effects, she said.

Nagel is four years into a study involving 200 kids in the Portland and Vancouver areas. She is tracking them from the time before they use any type of drugs or alcohol to young adulthood.

She s using brain scans to look for biological markers that may indicate whether a child will use drugs or alcohol.

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