Teen brains are more vulnerable to the effects of marijuana than alcohol, a new study finds.

Adolescents who begin using marijuana regularly may suffer lasting repercussions in their thinking ability, according to scientists at the University of Montreal.

“Cannabis causes cognitive impairment and delayed cognitive development in adolescents,” Patricia Conrad, the lead author and professor of psychiatry at the University of Montreal, told NBC News.

The study, published Wednesday in the American Journal of Psychiatry, followed over 3,800 adolescents from 31 Montreal-area schools over four years. The teens, who started participating in the study when they were 13, agreed to provide annual reports of how frequently they used marijuana and alcohol. They also took computer-based cognitive tests that measured recall memory, perceptual reasoning, inhibition and short-term memory.

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