Daily anxiety and depressive symptoms are associated with greater same-day cannabis-alcohol co-use than single-substance use among Black sexual and gender minority people

• Cannabis and alcohol co-use occurred on 20 % of days among Black SGM. • Mild to moderate anxiety/depression increased the likelihood of co-use. • Greater mental health symptoms were linked to more co-use than single-substance use. Rapidly changing cannabis legalization has contributed to increased cannabis use and co-use of cannabis and alcohol, including among sexual and gender minority people (SGM). Black SGM endure long-standing disparities in comorbidities of substance use, mental health, and other critical health outcomes, yet little is known about cannabis-alcohol co-use and its mental health correlates. This study examined associations of anxiety/depression symptoms with same-day cannabis-alcohol co-use among Black SGM. Data were obtained from the Neighborhoods and Networks Part 2 (N2P2) Study (2022–2024), a cohort of Black SGM aged 16–35 in Chicago, Illinois ( n = 617). Participants completed a 14-day ecological momentary assessment (EMA) of cannabis and alcohol use and mental health symptoms. Random-effect multinomial logistic regression models examined relationships of anxiety/depression and same-day cannabis-alcohol co-use. Across 5729 EMA days from 521 participants who completed ≥1 EMA daily survey, same-day cannabis-alcohol co-use, cannabis-only use, and alcohol-only use occurred on 19.8 %, 36.5 %, and 6.3 % of days, respectively. Elevated daily anxiety and/or depressive symptoms were reported on 20.9 % of days. Participants were more likely to report same-day co-use vs. no use on days with mild (aRR=1.5, 95 % CI: 1.2–1.9) or moderate (aRR=1.9, 95 % CI: 1.4–2.5) daily anxiety and/or depressive symptoms. Compared with single-substance use days, moderate general anxiety/depressive symptoms were more likely to be reported on co-use days (aRR=1.6, 95 % CI: 1.3–2.1). The findings underscore the additive comorbidity of mental health and same-day cannabis-alcohol co-use. Future research should identify subgroups at heightened risk and develop multilevel interventions addressing co-use and mental health among Black SGM.