The poll, conducted on the What They Play website, asked parents what they'd be most concerned about their 17-year-old child doing while at a sleepover. Marijuana use topped the poll at 49%, followed by playing Grand Theft Auto at 19%. Watching porn and drinking beer clocked in at 16% and 14%, respectively.

"Although these findings seem surprising at first, they hint at fears parents have about video games," said Grand Theft Childhood co-author Cheryl K. Olson. "To some parents, video games are full of unknowable dangers... Of course, parents don't want their children drinking alcohol, but that's a more familiar risk."

The accuracy of the poll, however, remains an area of dispute; though What They Play is a site most commonly referred to by concerned parents, the sampling method—a simple online poll—calls into question the legitimacy of the participants.

An earlier poll conducted by the website found that parents were most offended by a depiction of a heterosexual act in a video game at 37%, followed by two men kissing at 27%. Graphic violence—in this case, a severed head—clocked in third at 25%, while multiple vulgarity use brought up the rear at 9%.

A perennial favorite of media violence watchdog groups, the Grand Theft Auto series saw new heaps of controversy cropping up with the release of its latest iteration, Grand Theft Auto IV, earlier this year. Organizations such as the Parents Television Council and Mothers Against Drunk Driving have taken aim at the title.