Casual Pot Use Changes Young Brains Abnormalities seen in 'parts you don't want to mess with' By Rob Quinn, Newser Staff Posted Apr 16, 2014 4:04 AM CDT 177 comments Comments Even relatively light use could be a problem, researchers say. (AP Photo/Jeff Chiu, File) (Newser) – Even casual use of marijuana could be messing up young people's brains at a time of life when they need to make major decisions, a new study finds. Researchers say that people aged 18 to 25 who used marijuana at least once a week were found to have abnormalities in the parts of the brain linked to emotion, decision-making, and motivation, the Boston Globe reports. While it's not clear whether the changes are linked to decreased function, "this is a part of the brain you do not want to mess around with," the lead researcher warns. The casual tokers had an average of six joints a week, and the changes appeared to be more pronounced the more that was smoked. The changes in young brains are reason to worry, the lead researcher says, because "this is when you are making major decisions in your life, when you are choosing a major, starting a career, making long-lasting friendships and relationships." A neuropharmacologist not involved with the study says that while he doesn't doubt the results, he is wary of marijuana studies like this one that were funded by federal agencies tasked with limiting drug use. "If it were my child, even with this study, I'm more comfortable with young people having a marijuana habit than drinking regularly," he tells USA Today.