Adolescents sometimes raise important topics by putting adults on the spot. When asked if they have ever used marijuana, many parents feel surprised, defensive or wary. But with new research confirming that parents who provide direct information, guidance or advice about substances like marijuana have adolescents who are less likely to experiment with drugs, we might also feel grateful that our teenager has put the topic on the table.

Regardless of what your history is, it can help to receive “Did you smoke weed?” as an overture rather than an inquisition. Your teenager probably has more pressing questions lined up behind that one. Whether conscious of it or not, a teenager asking, “What choice did you make?” is often wondering, “What choice should I make?”

Dr. Jennifer Guss, a physician in Houston, said she faced the question when her daughter, Sofia, was in middle school. She explained why she had never tried marijuana but then asked what was on her daughter’s mind. She learned that Sofia was trying to make sense of the evolving marijuana laws, which gave her mother the opportunity to note that “just because something is legal doesn’t make it healthy and safe.”

Dr. Guss feels that her early candor with her daughter helped them continue to dip in and out of conversations about marijuana as Sofia entered high school when “the issue of drugs became more salient and visible around her.”

Sean Hice, a Cleveland-area businessman who was the first in his family to graduate from college, knew just what he wanted to say when his 13-year-old son asked him if he had ever smoked marijuana. He explained that drugs frightened him and that he didn’t want to do anything that could derail his plans to finish his business degree. “I told him that I waited until the second semester of my junior year when I had all the grades I needed in my major,” Mr. Hice said. “I knew I could pay off my loans and felt like I had control of my life before I tried it.”

Adults who themselves may not have carefully weighed the decision to smoke marijuana can still make the most of hindsight. They might say that they would have made a different choice had they known what we know now about the vulnerability of the teenage brain to cannabis. In the same vein, they could take the opportunity to note how very lucky they were that nothing went wrong, or to explain what did.

Parents sometimes worry that talking about their past use, or talking about illegal substances at all, might be taken as granting permission to experiment with drugs. If this is a concern, it can be addressed head on: “I did try pot, but I don’t want you to hear that as me saying that it’s O.K. for you. I want you to be smarter about it than I was.”

Other adults might welcome the opportunity to articulate the conditions under which they would give their blessing. For instance, the mother of a teenager in my practice said that she wouldn’t mind if her son tried marijuana, but only once he was in college, and only by smoking the supply of an uncle who grows his own. For parents who have no objections to cannabis use, questions about the past can open the door to discussions of what has changed in recent years, such as the growing availability of edible and concentrated forms of marijuana, and what hasn’t: recreational use of it is still illegal for minors in the United States.

Research consistently shows that adolescents take their parents’ guidance to heart even if they don’t always indicate as much. Regardless of the parent’s stance on marijuana use, it might be worth adding, “I’m asking you to be careful because I don’t want you to get hurt or find yourself on a path that you don’t mean to be on.”

The results of the same recent study on direct conversations about drugs suggest that personal or vicarious accounts of the downsides of substance use are especially compelling for teenagers. A parent who has a lot of stories to share might say, “Your grandparents were not paying attention when I was growing up and I got myself into situations that I should have never been in. When I became a parent I knew I wanted to do it differently. Let’s keep talking about this because I did enough learning for both of us.”

Some teenagers who ask about their parents’ past use are actually seeking the opposite of permission to try marijuana. They’re looking for reassurance that it’s O.K. not to. As one of my adolescent clients put it, “You can worry that you’re missing out on something — that it’s part of the ‘high school experience’ that a teenager is supposed to have.”

Mr. Hice addressed this concern by encouraging his son to see if he could have fun without using drugs and to “think about the pitfalls, your health, getting caught, getting expelled.” He also told his son that he watched his fraternity brothers closely both when they were high and also on the next day. From there Mr. Hice explained that, “it just didn’t look like the benefits outweighed the risks.”

Parents won’t always know what’s behind their teenager’s sudden interest in their personal choices and responding with either a detailed confessional or an abrupt, “That’s none of your business,” will probably make it harder to find out.

And adults who aren’t prepared to answer the opening question can still keep the lines of communication open, so long as “I’m not sure I’m ready to have this conversation” gently gives way to “but how come you’re asking?”