More teens are regularly using marijuana by vaping rather than smoking, even as mysterious lung illness claims young lives across the United States, according to a study released Wednesday.

Fourteen percent of high school seniors said they vaped marijuana in the previous month, according to the National Institutes of Health’s annual Monitoring the Future survey. That’s nearly double the rate from 2018, the second-largest annual increase recorded in the survey’s 45-year history. It’s also up dramatically from 4.9% in 2017.

The survey, conducted earlier this year, also found that 22% of high school seniors — about the same percentage as in 2018 — say they use marijuana, which can be smoked, vaped or eaten through an edible.

“It appears that kids are switching how they are using marijuana, not how much they are using marijuana,” said Ken Warner, an emeritus professor of health policy at the University of Michigan, who was not affiliated with the study.