Effects of Marijuana Use on Smokers Switching to Electronic Cigarettes

Electronic cigarettes (e-cigarettes) have received attention as a harm reduction strategy for smokers unable to quit. However, African American and Latinx smokers are less likely than Whites to switch exclusively to e-cigarettes, which could perpetuate a tobacco-related health disparity. Marijuana smoking is a known barrier to cigarette cessation and is associated with increased carbon monoxide (CO) exposure. The goal of the present study was to evaluate whether cigarette reduction and corresponding changes in short-term cardiopulmonary outcomes were attenuated by combustible marijuana use among smokers switching to e-cigarettes. This was a secondary analysis from a larger randomized controlled trial with 186 underrepresented minority cigarette smokers (92 African American and 94 Latinx) who were provided an e- cigarette for six weeks and encouraged to make a complete switch (n = 125) or assigned to a control group (n = 61). Results found marijuana smoking was not a barrier to harm reduction outcomes among smokers provided e-cigarettes compared to the control. Combustible marijuana use was linked with higher CO at week six (p .05) for both groups, but it did not qualify the association between study condition and CO. Marijuana smoking during this six-week harm- reduction trial was not linked with other outcomes: cigarettes smoked, respiratory symptoms, and lung function (ps .05). Noteworthy is that combustible marijuana use was related to the outcome of CO, a common biomarker used to define and verify exclusive switching status. A possible implication is reduced ability to bio-verify and identify exclusive switching among marijuana smokers, due to elevated CO from combustion. Further, higher CO among co-users suggests an additive effect that could exacerbate health risks.