Medicinal use and recreational use are entirely different, but yeah, recreational use affects the brain, especially in younger people. These studies are fairly new and somewhat inconsistent because of that, but the effects on the brain are sometimes similar to those of other drugs, especially with long-term use. I could find dozens of sources suggesting the same thing, but I JUST did that last week for a homework assignment. But anyone could find some with a quick search. They'll be a lot more recent, though.
Edit: Just for your entertainment...or maybe mine!
http://www.drugabuse.gov/publications/d ... /marijuanaJanuary 2014
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.
This was the first source of my search, but literally dozens will suggest the same thing. The effects on the brain are real. Real, I tell ya!
