How great is oral sex? So great that it increases the likelihood that teens who engage in it will have vaginal sex as well. This means oral sex is the marijuana of sex: A gateway to the good stuff.

According to a new study, conducted by Bonnie Halpern-Felsher of UC San Francisco and others, and based on a survey of 600 California high schoolers through 11th grade, most teenagers have their first oral sexes and their first vaginal sexes within six months of one another. Though the study couldn't tell which came first, for the most part the kids who'd only had one flavor of sex had oral and not vaginal.

Also—and, straight 13-year-olds, listen up—high schoolers who engaged in oral sex by the end of their first year had a 50 percent chance of engaging in vaginal sex by the end of their junior year. And, don't worry! This was true across racial, ethnic and gender boundaries.

[CBS News]