Survey confusion: 9% of vape users missed due to cannabis mix-up

People use similar devices to vape nicotine and cannabis, potentially causing misclassification error in surveys. This study aimed to (1) describe the degree of misclassification of people who vape cannabis as people who used electronic nicotine products (ENPs) in the past 30-days (P30D); and, (2) describe sociodemographic and tobacco use characteristics among people who vaped cannabis. Data were drawn from the Population Assessment of Tobacco and Health Study Wave 5 (2018-19). People who used ENPs in the P30D and stated that they used cannabis with an ENP (n = 5723) were asked how often this occurred ("every time", "most of the time", "sometimes", "rarely", "never"). We report weighted prevalence estimates of cannabis use frequency by sociodemographic characteristics and cigarette smoking status. Among adults, 8.9% [95% confidence interval (CI): 8.62-9.24] used ENPs in the P30D; among ENP consumers, 9.1% (95% CI: 8.23-10.05) used cannabis "every time." Excluding "every time" cannabis use, P30D ENP use was 7.7% (95% CI: 7.44-8.02). People who did not smoke tobacco cigarettes were more likely to vape cannabis "every time" (11.4%; 95% CI: 9.82-13.22) compared to people who previously (7.0%; 95% CI: 5.29-9.15) or currently (8.3%; 95% CI: 7.02-9.71) smoked cigarettes. Among people who used ENPs in the P30D, those who used cannabis "every time" had greater odds of being younger and identifying as lesbian, gay, bisexual, or something else, Black, or Hispanic. Improved methods are needed to differentiate between nicotine vaping and other types of vaping. Additionally, there is the potential for a greater degree of misclassification by individual characteristics. People who vape nicotine may also vape cannabis, but there has been little work to-date to understand how accurately surveys differentiate nicotine from cannabis vaping. Though the Population Assessment of Tobacco and Health Study survey clearly asks about nicotine use, 9.1% of people classified as using ENPs in the past 30-day ENP indicated that they were vaping cannabis "every time" with an ENP. The degree of misclassification of ENP use varied by sociodemographic and tobacco use characteristics. To fully understand ENP use, it is necessary to assess cannabis vaping. Failure to disentangle vaped nicotine from cannabis can over- or under-estimate these respective behaviors.