Discordant Reporting of Vaping of Cannabis among High School Seniors in the United States.

Introduction: 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.Methods: We examined combined data from the 2017-2019 Monitoring the Future nationally representative survey of high school seniors in the US (N = 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.Results: 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.Conclusions: 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.