Adolescent simultaneous use of alcohol and marijuana by trends in cigarette and nicotine vaping from 2000 to 2020

•From 2000–2020, SAM increased among students who have never smoked cigarettes or vaped nicotine, despite declining overall.•Despite declines in smoking, increase in vaping may reverse declining trends in simultaneous alcohol and marijuana use.•Marijuana use is increasing in US adolescents, whereas alcohol‐use‐only is declining.