As electronic cigarettes have proliferated and spawned a sub-culture of their own—vape shops, chai-latte-flavored vaping fluid and even the “sport” of cloud chasing—few policies have seemed as intuitive as stopping children under 18 from buying them.

As almost all e-cigarettes contain nicotine, they’re addictive. Because nicotine is a stimulant, vaping almost certainly has the potential to cause heart disease. E-cigarettes likely don’t cause cancer and lung disease (those come mostly from the burning that takes place in combustible cigarettes) but they certainly aren’t risk-free either. Since e-cigarettes are so new, finally, nobody can be certain about their long-term health impacts. Nonetheless, the policy of banning sales of e-cigarettes to children has support from anti-smoking groups, major tobacco companies, upstart vaping companies, vape-store owners and advocacy groups that speak for vapers. The only organized opposition to some state-level youth-sales bans has come, indeed, from anti-smoking groups that are suspicious of big tobacco’s support for them and want legislatures to pass other regulations or taxes at the same time.

That’s why it’s interesting and perhaps a bit distressing to note a new paper accepted by the Journal of Health Economics (but not yet formally published) and written by Yale University’s Abigail S. Friedman. The paper, dense with economic jargon and regression analysis, comes to a shocking conclusion: “bans on e-cigarette sales to minors yield a statistically significant 0.9 point increase in the recent smoking rate among 12 to 17 year olds.” The increase, she finds, is large enough to offset the overwhelming bulk of the decrease in youth smoking that has otherwise taken place. Friedman’s data, furthermore, stands up even when controlled for everything from smoking rates among 18-25 year olds to state cigarette taxes.

Because they contradict such a widely supported and uncontroversial policy, it’s difficult to know what to make of these findings. Laws banning e-cigarette sales to children are unlikely to be repealed outright where they already exist (no organized group supports doing so) and there’s something unseemly about letting 8-year olds do something that looks almost exactly like smoking to casual observers.

Nonetheless, the Friedman’s findings can’t be ignored. If banning e-cigarette sales to minors causing more of them to take up smoking, then the current policy trend is almost certainly a net negative for public health resulting in millions of cumulative years of lost life.

Friedman herself suggests investigating the possibility of allowing 16 year olds to purchase e-cigarettes but not conventional ones. That certainly seems like a worthwhile idea to explore even if though doing it would almost certainly increase the number of high-school students who vape. Even better, it might also be worth exploring efforts to nuance the message of anti-smoking education programs. While it’s almost certainly best for one’s health to abstain from the use of any nicotine product, letting schoolchildren know that e-cigarettes are less dangerous than combustibles could encourage those who end up using one of them to select a safer alternative. Almost no modern anti-smoking programs make the distinction even though it could save lives. Since about 20 percent of American adults smoke even after decades of stern public health warnings, after all, a totally nicotine-free society isn’t an obtainable goal and probably isn’t a desirable one anyway.

The biggest takeaway, however, may be this: government policies intended to promote public health, even policies with near-universal support, can sometimes have negative consequences. Regulation, even when just about everyone supports it, can literally be deadly.