According to the latest back-to-school survey by The at Columbia University (CASA Columbia), American teens who spend any time on social networking sites are more likely to drink, smoke, and take drugs.

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For the first time this year, the annual National Survey of American Attitudes on Substance Abuse XVI: Teens and Parents asked 12- to 17-year olds if--like millions of older folk--they like to waste time on Facebook, Myspace and other social nets.

The survey shows that 70 percent of teens--a population of about 17 million--spend some time on social networks in a typical day. Compared to the 30 percent of teens who aren't daily users, this group is five times as likely to use tobacco, three times as likely to use alcohol, and twice as likely to use marijuana, the survey says.

Teens who've seen substance abuse photos--such as images of kids using drugs, getting drunk, or passed out--on social networks are even more likely to drink and take drugs.