A new survey from Yale finds nearly one in five teens who use e-cigarettes have vaporized marijuana, hash oil, or other cannabis byproducts.

“These findings raise concerns about the lack of e-cigarette regulations and the potential use of e-cigarettes for purposes other than vaping nicotine,” concluded the authors.

Powered by batteries, e-cigarettes contain a heating element that vaporizes a liquid nicotine solution when inhaled. Among middle and high school students, "vaping" (as e-cigarette use is commonly called) has tripled between 2013 and 2014, according to a recent report from the Centers for Disease Control and Prevention (CDC). Findings from this National Youth Tobacco Survey show that during that one year period, vaping among high school students increased from 4.5 percent to 13.4 percent, a total of two million students. The CDC also reported tripling rates among middle school students: from 1.1 percent in 2013 to 3.9 percent, or 450,000 total students, in 2014.

While hash oil can be substituted for the nicotine solution in most of the regular e-cigarettes on the market, some electronic devices, noted the Yale researchers, have been specially designed for use with marijuana leaves or wax infused with THC, the psychedelic ingredient in marijuana. For the study, then, 3,847 Connecticut high school students were anonymously surveyed by the research team hoping to assess the use of cannabis by way of e-cigarettes.

Nearly 28 percent of the surveyed high school students reported using e-cigarettes in the current study, a much higher rate than listed in CDC's nationwide analysis. Among these e-cigarette users, those most likelely to vaporize cannabis included males, younger students, lifetime e-cigarette users, and lifetime cannabis users, said the Yale researchers.

Just under 20 percent of students using e-cigarettes reported vaporizing dried cannabis leaves with the device, study results indicated. Meanwhile, about 15 percent of this same group of students reported vaporizing hash oil, and 10 percent reported vaporizing wax infused with THC.

“The smell of vaping marijuana isn’t as strong as smoking it, plus the similarity in appearance of hash oil and nicotine solutions make this a really inconspicuous way of using marijuana,” Dr. Meghan E. Morean, lead author and currently an assistant professor of psychology at Oberlin College. Vaping concentrated liquid forms of marijuana can be much more potent than smoking dried leaves, she and her co-authors noted.

Source: Morean ME, Kong G, Camenga DR, et al. High School Students’ Use of Electronic Cigarettes to Vaporize Cannabis. Pediatrics. 2015.