LAUSR

To the Editor: C annabis is the most widely used illicit drug in the U.S. In 2018, 16% of Americans aged 12 years or older reported using cannabis. Vaping, or e-cigarette product use, is an emerging mode of cannabis use because of perceptions that it is less harmful than smoking and with better taste and a stronger ‘‘high.’’ Along with a range of health effects associated with cannabis use, chemicals, such as vitamin E acetate, present in some tetrahydrocannabinol (THC)-containing vaping products can be harmful, as demonstrated by the recent national outbreak of lung injury. Data are limited on vaping as a mode of use of cannabis as traditional public health data systems typically do not capture these behaviors. We conducted a retrospective observational study across 245 vaping and substance-use related message boards from 2015 to June 30th, 2019 (prior to the lung injury outbreak) on Reddit, the largest online forum site, having over an estimated 400 million users. Users make anonymous public posts, known as ‘‘submissions,’’ on topics of interest. Vaping and substance use are topics that have active online discussion communities and the prevalence of substance-related mentions correlates with public health indicators. We hypothesized that increases in discussions about vaping of THC-containing products were evident preceding the lung injury outbreak.