No, marijuana use doesn’t lower your IQ

The Washington Post (US)
Wednesday, October 22, 2014

A 2012 Duke University study made international headlines purporting to find a link between heavy marijuana use and IQ decline among teenagers. Other researchers questioned the findings immediately: Columbia University's Carl Hart noted the very small sample of heavy users (38) in the study. A follow-up study published 6 months later in the same journal found that the Duke paper failed to account for a number of confounding factors. A new study from the University College of London provides even stronger evidence that the Duke findings were flawed.