The FDA calls teen vaping an “epidemic,” but the influence of e-cigarettes on teens’ overall health might be more complicated than assumed, according to a new study out Thursday in the journal Tobacco Control. It suggests that while teens and young adults in the U.S. did start flocking to e-cigarettes these past few years, they also significantly cut back on smoking traditional tobacco cigarettes during the same time period. So could vaping be the silver bullet that kicks tobacco to the curb?

Vaping advocates have long claimed that e-cigarettes can and will help current smokers wean themselves away from smoking tobacco cigarettes, with the eventual goal of making it easier for them to quit nicotine altogether. But the evidence supporting this prediction has been mixed. A study earlier this year, for instance, found that adults who became dual users of e-cigarettes and tobacco cigarettes were actually less likely to quit their habit in a year’s time than people who only smoked cigarettes.

When it comes to teens, other research has found that vaping’s popularity has had no major positive effects on their smoking rates. Some studies have even suggested that vaping is creating new smokers, with teens who start vaping becoming more likely to eventually transition into tobacco than non-vaping teens.

But researchers behind current research say that past studies haven’t looked at teen vaping trends alongside smoking trends long enough for us to be sure of anything. So they decided to analyze and combine data from five different nationwide surveys of teens and young adults in the United States.

Mirroring other research, they found that vaping shot up in popularity around 2014 and has stayed popular in the years since. But they also found a faster, inverse drop in traditional smoking rates during those same years.

According to one survey of teen drug use, annual rates of any smoking in the past 30 days among 12th graders have been declining by 4.5 percent over the long term. But during 2014 to 2017 there was an additional 9.1 percent annual reduction of any level of smoking.

There are a few caveats to the study’s findings, though. Like other population studies, it can only tell us that an indirect connection between teen smoking and vaping exists, not whether one trend is directly impacting the other or vice versa.

“The most important takeaway from the study is that the public health implications of vaping are complex. We should not just focus on vaping, but should consider its effect on smoking,” he said. “Smoking presents far greater health risks, so that any reduction in smoking that arise as a result of vaping needs to be given strong consideration in evaluating any additional health risks that vaping may present.”