BACKGROUND AND AIMS: Adverse childhood experiences (ACEs) are linked to poor behavioural and mental health outcomes, including substance use, and disproportionately affect sexual and gender minorities (SGM). However, the relationship between ACEs and substance use in this population remains underexplored. This review investigates associations between ACEs and substance use outcomes in SGM adults.

DESIGN: Registered with PROSPERO (CRD42024493936), we systematically searched six databases from inception to 13 April 2025. Following PRISMA guidelines, two authors independently screened studies and extracted data comparing substance use outcomes in SGM adults with and without ACEs histories. Due to heterogeneity, we conducted a narrative synthesis. Risk of bias was assessed using the 2019 Mixed Methods Appraisal Tool (MMAT).

PARTICIPANTS AND MEASUREMENTS: Included studies involved SGM adults (≥18 years) who experienced at least one ACEs before age 18. SGM status encompassed lesbian, gay, bisexual, transgender, queer, intersex, non-binary, and other identities. Outcomes included any substance use (drug, alcohol, tobacco), with ACEs exposure as the primary variable.

FINDINGS: Thirty-two studies (N = 43,197) were included. Twenty-nine epidemiological studies showed consistent associations between ACEs and negative substance use outcomes across SGM sub-groups and substances. Three qualitative studies highlighted links between substance use and child sexual abuse, heterosexism, and intersecting oppressions such as racism and institutionalization.

CONCLUSIONS: ACEs are associated with adverse substance use outcomes in SGM adults. Further research is needed on how intersecting marginalizations shape these associations.