American teenagers are vaping, while their use of alcohol, cigarettes, cocaine, LSD, ecstasy, heroin, and opioid pills is dropping, according to University of Michigan researchers, the Associated Press reported.

The findings from this year’s teenage drug-use survey were based on responses from 45,000 students in grades 8, 10, and 12 across the country. More than 1 in 3 seniors last year vaped—smoked electronic cigarettes—which is 10 times the amount of regular cigarette smoking, according to the Guardian.

Twenty-one percent of high school seniors vaped nicotine this year, compared to just 11% last year, nearly double. More teens also vaped marijuana, with 7.5% of high school seniors saying they used vape pens for weed in the last month, compared to 4.9% last year.

“Teens are clearly attracted to the marketable technology and flavorings seen in vaping devices,” Dr. Nora D Volkow, director of the National Institute on Drug Abuse, told the Guardian. “However, it is urgent that teens understand the possible effects of vaping on overall health; the development of the teen brain; and the potential for addiction.“

Health officials are concerned about the rise in teen vaping for a number of reasons. For starters, nicotine is harmful to brain development. Further, some researchers are concerned that vaping will serve as a “gateway drug” to cigarettes and other drugs.

The study found a decline in teen use of other substances, including cigarettes, the use of which has dropped to its lowest level since 1975. Researchers in the UK have also found that as more adults smoke e-cigarettes, fewer adults are smoking cigarettes, the Guardian reported.