Alcohol and cannabis use and Co-use among U.S. sexual minority young adults: Findings from the 2019–2021 monitoring the future longitudinal panel data

Background Sexual minority (SM; e.g., lesbian, gay, bisexual) young adults report elevated substance use, yet few studies examine whether disparities extend to use newly-reported during young adulthood using behaviorally specific measures of daily use and co-use. Methods We analyzed Monitoring the Future Longitudinal Panel data (2019–2021; N = 12,173; 14.9% SM). Primary analyses used multivariable logistic regression to estimate incident-use odds during young adulthood among respondents reporting no lifetime alcohol and/or cannabis use at age 18. Outcomes included incident alcohol use, cannabis use, daily cannabis use, and past-30-day alcohol–cannabis co-use, defined as use of both substances in the past 30 days. Secondary analyses estimated prevalence and odds of past-30-day alcohol use, past-2-week binge drinking, past-30-day cannabis use, daily cannabis use, and co-use by sex and sexual identity. Results Gay males had the highest observed past-30-day alcohol use (80.8%) and binge drinking (42.1%), while bisexual females had significantly higher binge drinking (37.6%), past-30-day cannabis use (47.8%), daily cannabis use (19.2%), and co-use (40.9%) than heterosexual females. Lesbian females and bisexual males showed elevated prevalence, with more limited incidence elevations. Incident-use models showed elevated odds of newly-reported cannabis use and co-use among gay males and bisexual females; bisexual females also showed elevated odds of newly-reported alcohol use and daily cannabis use. Contrasts between SM subgroups were generally nonsignificant. Conclusions Incident-use disparities among SM young adults, particularly gay males and bisexual females, indicate that elevated substance use is not solely carried forward from adolescence. Young adulthood is therefore an important window for subgroup-specific intervention.