A USC study on teen marijuana use released Friday suggests that dosage and type of use play a determinative role in frequency, with cannabis concentrates leading to the heaviest use.

The findings, which appear in JAMA Network Open, may help direct cannabis control efforts and guide public education campaigns, said researcher Jessica Barrington-Trimis, assistant professor of preventive medicine at the USC Keck School of Medicine.

“We really wanted to understand whether the type of cannabis that youth experiment with influences the likelihood that they will continue to use cannabis and use more heavily,” Barrington-Trimis said.

“When we started this research, we were especially interested in the role of cannabis concentrates, which generally contain very high levels of THC (the psychoactive component in cannabis).”

Barrington-Trimis and her colleagues surveyed 2,685 adolescents with no history of heavy cannabis use from 10 Southland high schools. They asked 11th graders in spring 2016 about their use of five categories of cannabis products: combustible cannabis (pot, weed, hash, reefer); blunts (cannabis rolled in tobacco leaf or cigar casing); vaporized cannabis or hash oil via electronic vaping device (liquid pot, weed pen); cannabis or THC food or drinks (pot brownies, edibles); and cannabis concentrate (“dabbing” using wax, shatter, butane hash oil).

The researchers conducted 6-month and 12-month follow-up surveys in fall 2016 and spring 2017, when the students were in 12th grade. While the total number of dabbing users was low, research showed that those users were nearly six times more likely to still be using concentrates in the follow-ups, and had used concentrates an average of nine more days than those who didn’t use concentrates in the past 30 days when asked in the follow-ups.

Concentrates contain THC levels two to four times higher than that found in traditional cannabis products.

“It’s early exposure to the dose of THC used in adolescence that may be likely to drive continued use and increases in the frequency of use,” said Barrington-Trimis. “If someone picks up a vaporizer with a low level of THC, they may not be likely to keep using it. But with concentrates, the high level of THC may increase the likelihood that they continue to use and use more frequently.”

The study’s other authors include Junhan Cho, Esthelle Ewusi-Boisvert, Jennifer Unger and Adam Leventhal, all of USC; Deborah Hasin of Columbia University and Richard Miech of University of Michigan. It was funded by grants from the National Institute for Drug Abuse and the Tobacco Related Disease Research Program.

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