Youth who use marijuana once a week or more could be doing some serious damage to their brains, according to a study presented at the American Psychological Association’s annual convention earlier this month.

Researchers examined the brain capabilities of marijuana users under the age of 25 for the study. They found that those who smoked pot regularly suffered from loss of memory, cognitive abilities, poor attention spans and a decrease in IQ.

“It needs to be emphasized that regular cannabis use, defined here as once a week, is not safe and may result in addiction and neurocognitive damage, especially in youth,” wrote Krista Lisdahl, director of the brain-imaging and neuropsychology lab at the University of Wisconsin-Milwaukee.

These findings are pretty critical for two reasons: For one, Americans are becoming increasingly comfortable with the idea of legalizing the stuff. Pot has already been decriminalized in the states of Colorado and Washington, with several others in line to do the same. For another, pot use is particularly prevalent among the very people whom it might be harming the most—youth. Pot use begins in the late teen years, peaks around age 20 and then sinks when youth hit around age 25 or so.

“Is it a coincidence that use significantly goes down at 25 when the brain is at its full maturation?” Lisdahl says. “I don’t think so.” (USA Today)

Paul Asay has written for The Washington Post, Christianity Today, Beliefnet.com and The (Colorado Springs) Gazette. He writes about culture for PluggedIn and wrote the Batman book God on the Streets of Gotham (Tyndale). He recently collaborated with Jim Daly, president of Focus on the Family, on his book The Good Dad. He lives in Colorado Springs with wife, Wendy, and his two children. Follow him on Twitter.