Trends in typologies of concurrent alcohol, marijuana, and cigarette use among US adolescents: An ecological examination by sex and race/ethnicity.

•Concurrent substance use made up 40% of past-month use among U.S. adolescents.•Prevalence rates of substance-use typologies vary by race/ethnicity and sex.•Female adolescent users were most likely to be alcohol only users.•Marijuana only users were disproportionately African American and Hispanic.•African American youth are at high risk for concurrent alcohol and marijuana use.