Discordant report of vaping of cannabis among high school seniors in the United States.

: Reliable responses on surveys are important to ensure accurate estimates of drug use. This study compared prevalence of self-reported vaping of cannabis based on two separate questions on the same survey.: We examined combined data from the 2017-2019 Monitoring the Future nationally representative survey of high school seniors in the US (6,982). Students were first asked whether they had used cannabis in the past year via vaporizer in a section about cannabis use. Later on, students were asked about vaping behaviors, including cannabis vaping. Prevalence of self-reported vaping of cannabis was compared and a multivariable model delineated correlates of providing a discordant response - defined as reporting vaporizer use but not reporting vaping.: Estimated prevalence of use based on the question in the cannabis section was 11.9% (95% CI: 11.0-12.9) and prevalence based on the question in the vaping section was 13.2% (95% CI: 12.3-14.2). Among those reporting vaping of cannabis, 17.3% provided a discordant response. The corrected prevalence was 16.5% (95% CI: 15.5-17.6). Black students were more likely to provide a discordant report (aPR = 1.82, 95% CI: 1.23-2.69) and those reporting past-year vaping of nicotine (aPR = 0.27, 95% CI: 0.19-0.38) and/or nonmedical use of prescription stimulants (aPR = 0.44, 95% CI: 0.21-0.91) were less likely to provide a discordant report.: Self-report of vaping of cannabis varies depending on whether it is asked in a section about vaping practices or about overall cannabis use (use via vaporizer). Survey researchers need to consider how to best query cannabis vaping practices on surveys.