A fifth of high school students in the US who use e-cigarettes to vaporise nicotine are also using them to vaporise cannabis, a survey of almost 4,000 Connecticut teens revealed. Published in the scientific journal Pediatrics, the research provides concrete evidence that young people in the states are using e-cigs for marijuana, the team led by Meghan Morean of Oberlin College in Ohio claims.

"This is a relatively novel way of using marijuana, and kids are using it at a fairly high rate," said Morean. "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."

From surveying 3,847 students across five high schools in Connecticut, the researchers learned that 28% of students reported to using e-cigarettes, with 18.7% using the battery powered product to vaporize cannabis. The scientists add in their paper: "To better understand how students were using e-cigarettes or other portable vaporising devices to vaporize cannabis, we asked students: 'Which of the following have you used to smoke marijuana?'

"Answer choices included 'e-cigarettes filled with hash oil,' 'e-cigarettes filled with a wax plug,' 'portable vaporizers filled with dried marijuana (like a G-pen),' and 'other'. Students could select as many options as were applicable.

"Also of concern, the THC concentrations of vaporized hash oil and waxes can exceed that of dried cannabis by four to 30 times. The results of this study provide important evidence that high school students are using e-cigarettes to vaporize cannabis."