There’s a curious trend in the results from the latest Healthy Youth Survey, a comprehensive measure of Island teens’ attitudes and behaviors on a wide range of issues.

Ninety percent of the sixth-graders who answered the survey said they believe the adults in their neighborhood think marijuana use among young people is “very wrong.”

The number drops dramatically grade by grade, however. By the time seniors answer the question, a mere 5 percent say the adults they know consider marijuana use among young people wrong.

And don’t think our Vashon seniors are in sync with their peers on this score. Statewide, nearly 50 percent of 12th-graders report that the adults in their neighborhood disapprove of marijuana use among young people.

The numbers are similar for underage alcohol use, where 80 percent of the sixth-graders — compared to 12 percent of the seniors — say adults consider it very wrong.

Without follow-up interviews, it’s hard to know exactly what to make of these numbers, although the pattern is striking and suggests a troubling trend: Rightly or wrongly, our teens, as they grow older, hear a different message from the adults in their lives.

Certainly, our messages to the young people in our lives become more nuanced as they grow older. But those who are in the trenches on this issue — those who have shepherded our teens off to treatment centers or watched their lives unravel because of substance abuse — say there’s little room for subtlety or nuance when it comes to drug and alcohol use.

As Stephen Bogan, a therapist on Vashon, puts it, we need to draw a line in the sand. Adults need to tell young people not to use.

Undoubtly, some adults — especially on Vashon, where we’re known for our open-mindedness — feel it’s hypocritical to tell our kids not to smoke pot, since many of us did. There’s a huge difference, though. Over the last several years, marijuana growers have figured out ways to enhance the drug’s potency tremendously. Today’s pot, according to the National Institute on Drug Abuse, is 25 times more potent than that of a few decades ago. According to some experts, it’s a whole different drug.

Other adults may be hesitant to put forward a do-not-use message for fear it will only backfire. Better to at least keep our teens safe, they reason — to let them use at home, where we can keep an eye on them. But even that approach, experts say, is wrong. Someone in their lives, as Vashon youth advocate Yvonne Zick has often said, has to put forward a different message to counter the immense pressure our young people feel.

The job of parents, teachers and others is to erect some guardrails for our teens — so that as they go careening along the roads of teen life, there’s hope they’ll remain safe. And how do we put up those guardrails? According to Bogan, Zick and others in the field of prevention, we do so by being clear, unapologetic and consistent in our messages: We let them know that in fact we think it’s “very wrong” for our young people to use.