Teens who use tobacco, alcohol and marijuana are far more likely to try hard-core drugs like cocaine and heroin, according to a new study that calls the findings a "wake-up call for parents." The report, by Columbia University's Center on Addiction and Substance Abuse, included interviews with 30,000 American households. Some of the unsettling conclusions: kids aged 12 to 17 who used pot were 85 times likelier to use coke than those who never tried it; kids who drank were 50 times likelier; and kids who smoked were 19 times likelier. On the flipside, it found, 90 percent of all people who had ever tried cocaine had used all three"gateway" drugsfirst. Young people who abstain from tobacco, pot or alcohol are likely to never take up the harder stuff, the group claims.