Does Marijuana Harm the Brain?

Aug 14, 2014 |By Simon Makin

The Claim
Casual cannabis use harms young people’s brains.

The Facts
A study found differences in the brains of users and nonusers, but it did not establish that marijuana use caused the variations or that they had any functional significance.

The Details
Researchers at Northwestern University and Harvard Medical School conducted MRI scans of two groups of 20 young adults ages 18 to 25. One group reported using marijuana at least once a week, smoking 11 joints a week on average, whereas the other had used it less than five times total and not at all during the last year. Neither group had any psychiatric disorders, and the users were psychiatrically assessed as not dependent on the drug.

http://www.scientificamerican.com/article/does-marijuana-harm-the-brain/