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Marijuana Seen Changing Brain Behavior in Young Users

Heavy marijuana users had different brain shapes and lower IQs than non-smokers in a newly published study, suggesting a potential danger to young people who abuse the drug.

The research in this week’s Proceedings of the National Academy of Sciences used magnetic resonance imaging to measure people who used marijuana three times a day on average. The users had smaller amounts of gray matter and increased connectivity in the orbitofrontal cortex -- a section associated with decision-making and response to rewards -- and the changes were more pronounced in people who had started using earlier.