The number of teenagers vaping marijuana has risen dramatically within the past two years, increasing at a near-record pace, according to an analysis published Wednesday in the Journal of the American Medical Association.

In just one year's time — between 2018 and 2019 — the percentage of high school seniors who reported vaping pot within the past month rose from 7.5 percent to 14 percent.

The analysis looked at data from the Monitoring the Future survey, an annual report on drug use among 42,000 eighth, 10th- and 12th-grade students in 392 schools across the country.

The doubling of marijuana vaping rates in this year's report is the second-largest single-year jump for any substance since the survey began in 1975. The biggest increase was between 2017 and 2018, when nicotine use — driven by vaping — skyrocketed among teenagers. Researchers released data on 2019 teen nicotine vaping rates from the same survey back in September.

The new numbers illustrate "how rapidly vaping has permeated the culture of teenagers," said Dr. Nora Volkow, director of the National Institute on Drug Abuse, which funded the survey.

Seven percent of eighth graders reported vaping marijuana in 2019, up from 4.4 percent in 2018. Among 10th and 12th graders, the increases are nearly identical: 19.4 percent of high school sophomores and 20.8 percent of high school seniors said they vaped pot in 2019, up from 12.4 percent and 13.1 percent in 2018, respectively.

Some kids are vaping marijuana just about every day, the survey found: 3.5 percent of 12th graders, and 3 percent of 10th graders. Often, adults around them aren't aware of the drug use because dab pens and wax pens, as the devices are often called, are easily concealed and don't emit an odor.

There was no significant difference in usage among teens living in states that had passed laws legalizing recreational use of marijuana. But substance abuse experts say legalization of a substance can lead to a perceived drop in its risk, especially when it comes to teens.

"There's an impression that pot isn't addictive at all," said Dr. Sharon Levy, director of the adolescent substance use and addiction program at Boston Children's Hospital. "It's not uncommon for me to encounter kids, and sometimes even their parents, who haven't heard that these substances can be addictive."

What's more, teenagers' brains are still developing, making them particularly susceptible to the effects of nicotine and THC, the main psychoactive ingredient in marijuana.

Overall, the most commonly used illicit drug was marijuana in any form — a statistic that's remained steady for years. But since 2018, the number of eighth and 10th graders who said they use marijuana every day has risen significantly.

The health implications of so many young people vaping marijuana so frequently may not be known fully for years. Vaporizing THC and then inhaling it deep into the lungs has an effect on the body that's more potent than the rolled joints of previous generations.

Vaping devices came along in the early 2000s and "essentially perfected drug delivery," Levy said.

Vapes "can get the drug all the way down deep into your lungs, where the rich vascular bed absorbs these molecules very quickly, and sends a real shot of this stuff directly to your brain," Levy told NBC News. And because vape oils are often highly concentrated, a hit delivers a much higher dose than smoking would.

The dramatic rise in vaping comes at a time when other drug use among teenagers is falling. The Monitoring the Future survey found significant declines in abuse of opioids and medication for attention deficit hyperactivity disorder. Usage of LSD, cocaine and heroin was low among 12th graders, at 3.6 percent, 2.2 percent and 0.4 percent, respectively.

Though slightly more than half of high school seniors reported some alcohol use within the past year, the percentage is down from previous years. Reports of binge drinking also fell among 10th and 12th graders.

Just 2.4 percent of 12th graders reported smoking regular cigarettes, down from 3.6 percent in 2018.

Vaping, though, has become an epidemic among teenagers. When researchers asked 12th graders why they vaped any substance, most said they wanted to experiment and try the flavors. But a growing number of teens reported vaping "to relax or relieve tension." And the number of teens reporting they were "hooked" on the devices more than doubled, from 3.6 percent in 2018 to 8.1 percent in 2019.

Vaping has also been linked to more than 2,000 recent cases of severe lung illnesses called EVALI, e-cigarette or vaping associated lung injury. Most, but not all, have been linked to illicit THC vapes and weed pens.

"Those acute lung injuries are a reminder that sometimes we embrace technology without properly understanding it," Volkow said.

"We do not know the consequences of chronic delivery of very high temperature vapor into our lungs. After two, three, 10 years, it's likely to be quite deleterious," Volkow said, adding that regulation is necessary to control the quality of vape products on the market.

"Decades from now, we really don't want to be seeing that people in fact are suffering from severe inflammatory diseases of the lung that we have never seen before," she said.

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