The Brain on (Lots of) Marijuana

An interesting finding:

Marijuana’s effect on the brain is far from understood, but Australian research published Monday in the Archives of General Psychiatry suggests that very heavy long-term smoking might be associated with structural changes in two areas of the brain rich in receptors to the drug. The hippocampus, believed to regulate emotion and memory, and the amygdala, which plays a role in aggression and fear, were smaller—12 percent and 7 percent, respectively—in a group that smoked at least five joints daily for at least the past 10 years (and, on average, 20 years) when compared to a nonsmoking group.

Users also showed more signs of sub-threshold psychotic symptoms compared with those in the group that abstained. And on tests of memory and verbal ability, they performed more poorly. “Our findings suggest that everyone is vulnerable to potential changes in the brain, some memory problems, and psychiatric symptoms if they use heavily enough and for long enough,” says lead author Murat Yucel of the ORYGEN Research Centre and Melbourne Neuropsychiatry Centre at the University of Melbourne.

With a caveat:

But it’s way too early for parents to conclude that pot deteriorates the brain, cautions Scott Swartzwelder, professor of psychiatry and behavioral sciences at Duke University whose own research focuses on substance abuse and the adolescent brain. “Scientifically, it’s a very limited set of data,” he says. The study was tiny—it covered only 15 pot smokers and 16 abstainers—and looked at extreme behavior, so “I’m not sure how relevant it is to the general public,” says Swartzwelder, who is coauthor of Just Say Know: Talking to Kids About Drugs and Alcohol and Buzzed: The Straight Facts About the Most Used and Abused Drugs From Alcohol to Ecstasy (an updated third edition is being released in August). [NOTE: A great book with dispassionate and reliable information.]