Abstract
PURPOSE: Perceived harm is associated with substance use. Changes in product and policy landscapes may impact perceived harms of tobacco and cannabis. This study aimed to examine changes in young adults' perceived harms of tobacco and cannabis and their associations with use behavior during a period including both before and after legalization of cannabis. METHODS: We conducted a panel survey of California Bay Area young adults (mean age = 23.5 years old, 64.4% female) in 2014 and 2019-2020. Participants (N = 306) reported past 30-day use and perceived harms of tobacco and cannabis at both waves. Perceived harms to health of cannabis and tobacco (cigarettes, e-cigarettes, hookah, smokeless tobacco, and secondhand tobacco smoke) were measured from 1-"Not at all harmful" to 7-"Extremely harmful." Mixed-effects logistic regressions examined associations between perceived harms and use of tobacco and cannabis, controlling for demographics. RESULTS: Participants perceived lower harm for cannabis than for tobacco products. Perceived harms of e-cigarettes, hookah, and smokeless tobacco significantly increased over time; while perceived harms of cigarettes, secondhand tobacco smoke, and cannabis did not change. Increased perceived harm of e-cigarettes was associated with lower odds of any tobacco use (OR = 0.72, 95%CI = 0.56, 0.92), and increased perceived harm of cannabis was associated with lower odds of any cannabis use (OR = 0.51, 95%CI = 0.42, 0.62). CONCLUSIONS: Findings suggest that perceived harms of e-cigarettes and cannabis play important roles in driving young adult use behaviors. Risk communication efforts that increase perceptions of health harms related to e-cigarettes and cannabis may decrease use of tobacco and cannabis among young people.