Two times as many American high school students used nicotine-added electronic cigarettes in 2018 compared to the number of high school users last year.

That information comes from a new study about teenage smoking, drinking and drug use in the United States.

It was the largest single-year increase in the history of the study, which has been done in each of the past 44 years. It also was much greater than an increase in marijuana smoking during the 1970s.

FILE - A high school student uses a vaping device near a school campus in Cambridge, Mass.

The findings were released on Monday. They confirm the findings of a U.S. government survey completed earlier this year. That survey also found a sharp rise in vaping among children. It led federal officials to request measures that make it harder for children to get vaping products.

Experts blame the increase on newer e-cigarettes that look like computer flash drives and can be hard for adults to recognize.

Trina Hale goes to South Charleston High School in West Virginia. She told The Associated Press that vaping increased a lot at her school this year. She said that students seem to like the vaping products made by Juul Labs.

"They can do it wherever, whenever," she said.

Olivia Turman attends Cabell Midland High School in Ona, West Virginia. She said she has seen other students "hit their vape in class."

The government supported survey was a project of researchers at the University of Michigan. The latest findings are based on answers provided by about 45,000 students in grades 8, 10 and 12 in U.S. schools. It found that 1 in 5 high school seniors reported having vaped nicotine in the past month.

After vaping and alcohol, the most common drug teenagers use is marijuana, the survey found. About 1 in 4 students said they had used marijuana at least once in the past year. Marijuana use was more common in older children. Nearly 1 in 17 high school seniors said they use marijuana every day.

Marijuana smoking is about the same level as it was the past few years. Vaping of marijuana rose, however.

More teens are saying "no" to lots of other substances. The report noted a drop in usage of alcoholic drinks, cigarettes, opioid pills and the drugs cocaine, LSD, ecstasy and heroin.

Experts say it is not clear why so many young people are saying "no" at this time. The nation, as a whole, is in the middle of a deadly drug epidemic, mainly from opioids.

"What is it that we're doing right with teenagers that we're not doing with adults?" said Doctor Nora Volkow. She is the director of the National Institute on Drug Abuse.

One theory is that young people today are staying home and communicating on cell phones or other electronic devices. In earlier times, they would have socialized together in groups to smoke, drink and try 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 studies alcohol use.

The vaping increase is a big worry, however. Health officials say nicotine can harm developing brains. Some researchers also believe vaping will make young people more likely to use cigarettes, and perhaps later try other drugs.

But that has yet to happen, surveys show. But vaping products are new, noted Richard Miech, who directed the Michigan survey.

If vaping does lead to cigarette use among young people, that may start to show up in the survey as early as next year, he added.

The Associated Press reported this story. Susan Shand adapted it for Learning English. The editor was George Grow.

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