The use of flavored tobacco products is on the rise among middle and high school students because of e-cigarettes, according to a new study.

Among teens who use tobacco, the proportion using flavored products fell from 69.4 percent in 2014 to 57.7 percent in 2016, but then increased to 63.6 percent in 2017, UPI reports.

“Currently, there are no restrictions on the marketing and sales of flavored non-cigarette tobacco products. This has led to a proliferation of flavored tobacco products in the marketplace,” said lead researcher Hongying Dai of the College of Public Health at the University of Nebraska Medical Center. “Flavoring has become one of the leading reasons for current tobacco use among youth.”

E-cigarette use among teens has risen dramatically in the past year, according to the annual Monitoring the Future survey. Increases in teen vaping from 2017 to 2018 were the largest ever recorded in the past 43 years for any teen substance use in the United States, the survey found. The percentage of 12th grade students who reported vaping nicotine in the past 30 days almost doubled—from 11 percent to 21 percent.