Sexual orientation and gender identity disparities in substance use disorders during young adulthood in a United States longitudinal cohort

•Sexual minority young adults had elevated prevalence of past 12-month SUDs.•Sexual minorities were more likely to evidence multiple co-occurring SUDs.•Orientation disparities in SUDs were larger in people assigned female at birth.•Gender-identity differences in SUDs were smaller than sexual-orientation differences.•Future research on SUDs should include sexual orientation and gender identity. This study examined associations of sexual orientation and gender identity with prevalence of substance use disorders (SUDs) and co-occurring multiple SUDs in the past 12-months during young adulthood in a United States longitudinal cohort. Questionnaires self-administered in 2010 and 2015 assessed probable past 12-month nicotine dependence, alcohol abuse and dependence, and drug abuse and dependence among 12,428 participants of an ongoing cohort study when they were ages 20–35 years. Binary or multinomial logistic regressions using generalized estimating equations were used to estimate differences by sexual orientation and gender identity in the odds of SUDs and multiple SUDs, stratified by sex assigned at birth. Compared with completely heterosexuals (CH), sexual minority (SM; i.e., mostly heterosexual, bisexual, lesbian/gay) participants were generally more likely to have a SUD, including multiple SUDs. Among participants assigned female at birth, adjusted odds ratios (AORs) for SUDs comparing SMs to CHs ranged from 1.61 to 6.97 (ps