Research finds that marijuana use takes toll on adolescent brain function / EurekAlert, 13 October 2008
http://www.eurekalert.org/pub_releases/2008-10/uoc-rft101308.php
"Brain imaging shows that the brains of teens that use marijuana are working harder than the brains of their peers who abstain from the drug. At the 2008 annual meeting of the American Academy of Pediatrics in Boston, Mass., Krista Lisdahl Medina, a University of Cincinnati assistant professor of psychology, presented collaborative research with Susan Tapert, associate professor of psychiatry at the University of California, San Diego."