Twice as many high school students used nicotine-tinged electronic cigarettes this year compared with last year, an unprecedented jump in a large annual survey of teen smoking, drinking and drug use.
It was the largest single-year increase in the survey's 44-year history, far surpassing a mid-1970s surge in marijuana smoking.
The findings, released Monday, echo those of a government survey earlier this year. That survey also found a dramatic rise in vaping among children and prompted federal regulators to press for measures that make it harder for kids to get them.
Experts attribute the jump to newer versions of e-cigarettes, like those by Juul Labs Inc. that resemble computer flash drives and can be used discreetly.
Trina Hale, a junior at South Charleston High School in West Virginia, said vaping - specifically Juul - exploded at her school this year.
"They can put it in their sleeve or their pocket. They can do it wherever, whenever. They can do it in class if they're sneaky about it," she said.
Olivia Turman, a freshman at Cabell Midland High School in Ona, West Virginia, said she too has seen kids "hit their vape in class."
The federally funded survey released Monday is conducted by University of Michigan researchers and has been operating since 1975. This year's findings are based on responses from about 45,000 students in grades 8, 10 and 12 in schools across the country. It found 1 in 5 high school seniors reported having vaped nicotine in the previous month.
After vaping and alcohol, the most common thing teens use is marijuana, the survey found. About 1 in 4 students said they'd used marijuana at least once in the past year. It was more common in older kids - about 1 in 17 high school seniors said they use marijuana every day.
Overall, marijuana smoking is about the same level as it was the past few years. Vaping of marijuana rose, however.
More teens, however, are saying no to lots of other substances. Usage of alcohol, cigarettes, cocaine, LSD, ecstasy, heroin and opioid pills all declined.
Experts say it's not clear what's behind those trends, especially since the nation is in the midst of the deadliest drug overdose epidemic ever.
"What is it that we're doing right with teenagers that we're not doing with adults?" said Dr. Nora Volkow, director of the National Institute on Drug Abuse, a federal agency that funds the Michigan study.
One leading theory is that kids today are staying home and communicating on smartphones rather than hanging out and smoking, drinking or trying drugs.
"Drug experimentation is a group activity," Volkow said.
What about vaping? "Vaping mostly is an individual activity," said David Jernigan, a Boston University researcher who tracks alcohol use.
The vaping explosion is a big worry, however. Health officials say nicotine is harmful to developing brains. Some researchers also believe vaping will make kids more likely to take up cigarettes, and perhaps later try other drugs.
So far that hasn't happened, surveys show. But the Juul phenomenon is recent, noted Richard Miech, who oversees the Michigan survey.
If vaping does lead to cigarette use among teens, that may start to show up in the survey as early as next year, he added.
Last month, days after reports the Food and Drug Administration was planning to propose further restrictions on the sale of e-cigarettes, the Juul Labs announced it was taking steps to curtail the use of its flavored products by teens.
The company said it would stop selling its flavored pods — mango, cucumber, creme and fruit — at more than 90,000 retail stores nationwide, including convenience stores and specialty vape shops. The company also said it is shutting down some of its social media accounts, which are popular with young people.
In a statement, Juul CEO Kevin Burns said the company and the FDA "share a common goal – preventing youth from initiating on nicotine."
"We don't want anyone who doesn't smoke, or already use nicotine, to use Juul products. We certainly don't want youth using the product," he said. "It is bad for public health, and it is bad for our mission."
Juul holds more than 70 percent of the e-cigarette market share.