And yet, that's not to say that what kids see on TV or on the Internet doesn't affect them, Gilbert said.
About half of teens who regularly use social networking sites said they've seen pictures of kids drunk, passed out or using drugs on these sites, according to the survey. Seeing those images may reinforce the idea that "everybody's doing it," he said.
"There is no question the Web makes information available to youngsters. They know how to get information on drugs. There is also no question that through social media like Facebook they can see what other students are doing," Gilbert said. "If they see that, in fact, others are smoking dope, it makes it seem to be a rite of passage."
There also may be other reasons why the 30 percent of kids who don't use social networking are abstaining, including the possibility that they're growing up in very religious families or in homes where ethnic traditions dictate that children be highly supervised, Gilbert added.
The survey also found that nine in 10 parents don't think that spending time on social networking sites increases the likelihood kids will drink or use drugs, and only 64 percent of parents whose kids use social networking sites monitor their use.
"Parents should be looking at what their kids are watching on television and, secondly, what they are watching on social networks," said Joseph Califano Jr., founder and chairman of the National Center on Addiction and Substance Abuse.
In other findings:
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