Your kid is that age—he's either curious about consuming alcohol or perhaps already does. Until now, many experts have advised teaching your teen to use alcohol wisely, only occasionally and only in your presence, since there are pretty good odds he'll do it on the sly otherwise. But now, new research has led to a sea change in this thinking: Teenagers should not drink, because one drink often leads to more, and because the damage alcohol does to the adolescent brain could be pronounced and possibly lifelong.

It turns out that, although the brain doesn't get much bigger through the teen years, it continues to develop and strengthen well into the twenties, according to groundbreaking research that began at the National Institutes of Health in the 1990s.These changes take place mostly in the brain's frontal lobe, an area that helps us make decisions, plan for the future and control impulses, says Aaron White, PhD, an assistant research professor at Duke University Medical Center, who has studied teens and alcohol. "When teens drink, alcohol could disrupt development at a time when they're making important decisions about their future."

Alcohol also affects how the brain turns information into long-term memory, a critical process for enabling students to learn. "In our studies, if teens drank enough to feel shaky or nauseous or to have a headache the next day, they appeared to have dangerously affected their brains," says researcher Susan Tapert, PhD, an associate professor of psychiatry at the University of California, San Diego (UCSD). "Girls who drank too much had particular problems with visual/spatial functioning—the ability to read a map or put together a bookshelf. In boys, the ability to learn and retain verbal information was affected to a stronger extent than in girls.

"While the effects of alcohol on the brain are still being investigated, some dangers of underage drinking are clear: Every day, three teens are killed in accidents due to drinking and driving, and six more die in alcohol-related incidents such as drowning and suicide. And kids who drink are more likely to have other problems, like trouble in school or with the law or proneness to using illicit drugs. Plus, the younger kids are when they start to drink, the worse off they are. Those who begin drinking before age 15 are four times more likely to develop alcohol dependence than those who don't drink before age 20, according to the National Institute on Alcohol Abuse and Alcoholism (NIAAA). Yet four out of ten students have consumed alcohol by the end of eighth grade. Three out of four high school seniors say they've consumed alcohol, and nearly two thirds admit to being drunk at least once, according to a 2005 University of Michigan survey of 50,000 students.    

The good news is that teen binge drinking has decreased in recent years. Also encouraging: Adolescents who stop drinking lower their risk for related problems. But will stopping reverse the effects of alcohol on their brain? No one knows for sure. "Evidence suggests that if you drink heavily as a teen, once you become an adult, anything you've done to your brain you're probably stuck with," says Dr. White. "Adult alcoholics show some recovery of cognitive function after they stop drinking. But with adolescents, it's not about losing skills—it's about failing to develop them."

So how do you prevent your child from drinking? Should you stop drinking yourself and remove all alcohol from your house? Even if you did, there would be opportunities to drink elsewhere. "Our society condones alcohol for adults. There's even evidence that drinking a little is healthy for you," says Vivian Faden, PhD, deputy director of the division of epidemiology and prevention research at NIAAA. "Many parents have alcohol at home and enjoy it. So the message about drinking has to be more nuanced." There is no consensus on prevention. But experts suggest that you have age-appropriate talks with your children even before they start school (though it's never too late to start). These talks should be ongoing and help them see that moderate drinking is safe for adults, but, because kids' brains are still developing, it may not be safe for them.

Alcohol's lure can be potent. Its promises of confidence, coolness and popularity permeate our society. A magic potion for teens, it appears—but as with all potions, the magic wears off. As a parent, your job is to help your teen negotiate the slippery slope of alcohol consumption and discover the magic within him so he can become the successful, well-loved adult you know he can be.

What You Can Do

 Establish a firm policy for your child. "Parents who have a relaxed attitude about underage drinking or serve alcohol to their children are more likely to have children who grow up to have drinking problems," says Dr. White. "In fact, new research shows that thirty-four out of thirty-five European countries, where alcohol with meals is more common even for young teens, have higher levels of teenage binge drinking than the United States. Sure, some children will come out unscathed from this kind of upbringing, but why risk it?" Instead, adopt a firm family policy that includes clear consequences your teen can expect if he's caught drinking.

Set an example of moderation. You don't have to stop drinking yourself when your child turns 13. There's no evidence that teens whose parents imbibe moderately are more likely to drink themselves than those with parents who abstain. "Follow the rules of the dietary guidelines for moderate consumption of alcohol," suggests Dr. Faden. "That's no more than one drink per day for women and two drinks per day for men."

Help your child develop media savvy. Advertisers want your teen to believe he'll be cooler and smarter and attract more beautiful women if he drinks than if he doesn't. "As you watch TV with your teen, point out the truth: Drinking can cause impotence and make people look stupid, slur their words and abandon good judgment," suggests Dr. White. "There's nothing that kids hate more than being manipulated."

Encourage varied activities. Research from UCSD has found that kids are less likely to drink if they participate in volunteer activities, sports, drama or anything that helps them gain a sense of mastery.

Know your teen's friends. You don't want your child hanging out in homes where parents have a lax attitude about underage drinking. Some communities establish "safe home" networks, in which parents pledge not to serve alcohol to teens; when your teen mentions a new name, you can review the list of participating families to see if the parents have signed the pledge. Point out to your teen that even if he doesn't drink, he may get into trouble with the law or at school just by being around kids who do. "Establish a 'no questions asked' policy," says Dr. White. "If your teen is at a party where kids drink, he can call you for a ride home, and you won't ask him about it until the next morning."