AIM
To quantify the trends in frequent and occasional cannabis vaping, demographic differences and concurrent nicotine and alcohol use.

DESIGN
Observational study. Survey-weighted multinomial logistic regression models assessed trends and disparities in past 30-day cannabis use. Trends were assessed overall and by sex, race/ethnicity, parental education and urbanicity. Multinomial logistic regression models also estimated associations of cannabis use (none, use without vaping, use with vaping) with past 2-week binge drinking and past 30-day nicotine/tobacco use.

SETTING
United States, 2017-19.

PARTICIPANTS
Participants in the national Monitoring the Future (n = 51 052) survey.

MEASUREMENTS
Past 30-day frequent cannabis use (six or more times/30 days) and past 30-day occasional use (one to five times/30 days), with and without vaping.

FINDINGS
Past 30-day frequent cannabis use with vaping and occasional use with vaping rose from 2017 to 2019. Past 30-day frequent and occasional cannabis use without vaping declined. Certain groups, such as Hispanic/Latino or lower socio-economic status adolescents, experienced particularly notable increases in frequent cannabis use with vaping (e.g. prevalence among Hispanic/Latino adolescents). Adolescents who reported smoking and vaping nicotine, and 10+ occasions of binge drinking, were 42.28 [95% confidence interval (CI) = 33.14-53.93] and 10.09 (95% CI = 4.51-22.53) times more likely to report past 30-day cannabis use with vaping, respectively, compared with no use.

DISCUSSION
Cannabis use without vaping appears to be declining among adolescents in the United States, while cannabis use with vaping is accelerating; frequent cannabis vaping is especially increasing, with consistent increases across almost all adolescent demographic groups. Cannabis use among US adolescents remains highly associated with other substance use.