A new study shows that young adults who smoke marijuana--even just recreationally--had marked abnormalities in areas of their brains that regulate emotion and motivation.
For those young people -- and their parents -- who think that smoking pot in moderation isn't harmful, it's time to think again.
A study released by researchers from Northwestern University's Feinberg School of Medicine and Harvard Medical School has found that 18- to 25-year-olds who smoke marijuana only recreationally showed significant abnormalities in the brain.
"There is this general perspective out there that using marijuana recreationally is not a problem -- that it is a safe drug," says Anne Blood, an assistant professor at Harvard Medical School and the co-senior author of the study, which is being published in the Journal of Neuroscience. "We are seeing that this is not the case."
The scientists say theirs is the first study to examine the relationship between casual use of marijuana in young people and pot's effects on two parts of the brain that regulate emotion and motivation. As such, it is sure to challenge many people's assumptions that smoking a joint or two on the weekends is no big deal.
The new Northwestern-Harvard study punches a hole in conventional wisdom. Through three different methods of neuroimaging analysis, the scientists examined the brains of 40 young adult students from Boston-area colleges: 20 who smoked marijuana casually -- four times a week on average -- and 20 who didn't use pot at all.
The scientists examined two key parts of the brain -- the nucleus accumbens and the amygdala, which together help control whether people judge things to be rewarding or aversive and, in turn, whether they experience pleasure or pain from them.
The researchers found that among all 20 casual marijuana smokers in their study -- even the seven who smoked just one joint per week -- the nucleus accumbens and amygdala showed changes in density, volume and shape. The scientists also discovered that the more pot the young people smoked, the greater the abnormalities.