Marijuana on the brain

Marijuana also affects brain development, and when it is used heavily by young people, its effects on thinking and memory may last a long time or even be permanent. A recent study of marijuana users who began using in adolescence revealed substantially reduced connectivity among brain areas responsible for learning and memory. And a large long-term study in New Zealand showed that people who began smoking marijuana heavily in their teens lost an average of 8 points in IQ between age 13 and age 38. Importantly, the lost cognitive abilities were not fully restored in those who quit smoking marijuana as adults. Those who started smoking marijuana in adulthood did not show significant IQ declines. Drug facts, Marijuana http://www.drugabuse.gov/publications/drugfacts/marijuana

http://www.usatoday.com/story/news/nation/2012/12/06/nih-marijuana-effects/1751011/