NEW YORK >> About 1 out of 5 high school students in the U.S. say they vaped marijuana in the past year, and its popularity has been booming faster than nicotine vaping, according to a report released Wednesday.

“The speed at which kids are taking up this behavior is very worrisome,” said Dr. Nora Volkow of the National Institute on Drug Abuse, the federal agency that pays for the large annual teen survey.

Electronic cigarettes and other battery-powered vaping devices mostly heat a liquid containing nicotine into a vapor that’s inhaled, In recent years, they have been increasingly used to vaporize THC, the chemical that gives pot its high.

The University of Michigan survey asks students in grades 8, 10 and 12 across the country about smoking, drinking and drugs. About two-thirds of this year’s 42,000 participants were asked about vaping marijuana.

Vaping nicotine is still more popular: about 1 in 4 high schoolers said they had done it at least once in the previous year. But vaping marijuana grew more quickly: 1 in 5 high schoolers had done it at least once the year before.

About 1 in 7 high school seniors this year were considered current users of marijuana vaping — they had vaped in the month before they took the survey. That’s almost doubled from 1 in 13 the year before.

Overall, marijuana use — in all its forms — is holding steady. It’s not clear if students are switching to vaping or continuing to use other forms as well, said Richard Miech, who oversees the survey.

Daily marijuana use rose in both middle school and high school kids in 2019, and “if you want to be a daily marijuana user, vaping makes it easier,” he said.

It’s odorless and slips easily into a pocket. “You can just kind of graze on that all day,” he said.

The survey is in the Journal of the American Medical Association, which also published results of a different survey in 2018 that showed an increase in marijuana vaping among middle and high school students.

Both have limitations: the surveys rely on what kids say, and it does not include teens who are not in school. Federal and state laws ban minors from using marijuana recreationally, and prohibits sale of vaping products to kids

The Michigan survey was conducted earlier this year, before reports of a surge in cases of vaping-related lung damage, mostly in teens and young adults who used black-market THC products.

Volkow said the illnesses “may scare some teenagers away” from vaping marijuana.

The survey also found most other forms of teen drug use are flat or declining, including alcohol, ecstasy, heroin, cocaine, and meth. An exception was LSD, which has been increasing in 10th and 12th graders. About 3.6% of high school seniors said they’d dropped acid in the previous year.