ELIZABETH D’AMICO, RAND Corporation:

Among family and friends, I'm regarded as the Dear Abby of adolescent so-called bad behavior.

Here's the reason why. Because I have researched alcohol and drug use among teens for more than 20 years, and I'm a parent, people always assume I have devised a foolproof strategy for talking to kids about such issues.

Lately, I have been fielding a lot of questions about marijuana legalization.

I do feel like I have an edge when it comes to talking to my kids about marijuana. But, sometimes, it seems like I am sharing information on the fly, as I drive my kids down a busy L.A. street to school.

Since recreational marijuana was legalized in California last fall, a new billboards pop up all the time to advertise the fine art of smoking weed and where to buy it.

This leads my kids, 11 and 13, to ask a lot of questions: Why do people smoke marijuana? It can't be bad if it's legal and they can advertise, right, mom?

As always, it is best to give balanced, honest answers based on facts. Why do people smoke marijuana? Some may smoke it for medical reasons, to help with pain. Others may smoke it recreationally.

Parents might liken it to alcohol. You know how some people have a glass of wine with dinner to relax? Now some may smoke pot for the same reason.

But it's also important that your kids know that getting can change their mood and behavior. And just like alcohol, tell your kids it's illegal to drive after you have smoked pot.

I tell my kids the main reason that marijuana is illegal for those under 21 is because their brains are still developing, and marijuana can affect their concentration and memory. It may mean you don't do as well in school. That can mean fewer opportunities, like getting a good job.

Given this changing legal landscape, my kids and yours are going to be exposed to marijuana as frequently as they are to alcohol. And now that it's legal, here come the marketing campaigns, which all make smoking pot seem normal.

And just like alcohol and tobacco ads, marijuana ads may influence their choices. My own research has shown that middle school kids who reported seeing ads for medical marijuana were more likely to report smoking pot one year later.

You can't just say, don't do it. But you can get the facts, share them with your kids, and help them make a healthy choice.