By Rebecca Chasnovitz, M.D.:

When it comes to telling your kids about how you used drugs but they shouldn't, honesty may not be the best policy.

Researchers at the University of Illinois at Urbana-Champaign surveyed 561 middle school students on conversations they had with their parents about alcohol, cigarettes and marijuana. They found that children were less likely to think drugs were bad if their parents opened up with them about past substance use to teach a lesson. Children whose parents told them to avoid drugs were more likely to avoid them.

"Parents should really hit on what are the bad things that can happen, health-wise, from using drugs," said communications researcher Jennifer Kam, one of the study authors. "They should really clearly tell kids that they disapprove of them using drugs. Also, give them strategies to avoid use or decline use in a way that makes them look cool."

Other factors that discouraged drug acceptance in the middle school students included having parents who set rules against drugs and shared cautionary tales about other people who have gotten into trouble because of drugs, Kam said.

Parents who have engaged in drugs and alcohol in the past walk a fine line between lying to their children and divulging information that makes substance use seem acceptable.

"I would caution against lying," Kam said. "I wouldn't volunteer the information, but if a child asks, and a parent lies, it could impact the relationship later on."

The research showed an association between parent conversations and children's beliefs about drugs, but not that one necessarily caused the other. The study was also limited to white and Hispanic students from rural Illinois schools, so it doesn't capture possible regional and ethnic differences that would be present in other populations.

The Partnership for a Drug Free America agrees that parents should be honest and specific if a teen asks directly about past drug use, according to its Parent's Guide to the Teen Brain.

"You don't have to tell her all the details," the guide says. "Find out why she's asking about your history, and then tell her what she wants to know - nothing more."