PURPOSE: Adverse childhood experiences (ACEs) increase the risk for poor mental health (MH) and substance use. We describe relationships between adolescents' ACEs, substance use, and poor MH occurring during the COVID-19 pandemic. METHODS: We conducted a secondary analysis of data among U.S. high school students aged <
18 years, who participated in the nationally representative Adolescent Behaviors and Experiences Survey. Data were collected from January to June 2021. Bivariate and multivariable analyses assessed associations between individual ACEs (physical, emotional abuse by parent or caregiver, parent or caregiver job loss, food insecurity, sexual violence, physical dating violence, or cyber bullying) and cumulative ACEs (0, 1-2, 3, 4+) experienced during the pandemic and substance use
stratified analyses assessed effects of poor MH on associations between ACEs and substance use. RESULTS: Use of all substances was higher among adolescents with ACEs, particularly those who experienced both ACEs and poor MH during the COVID-19 pandemic. Prevalence of substance use was especially high among adolescents exposed to any sexual violence or physical dating violence. Compared to adolescents without ACEs, a higher percentage of adolescents with 4+ ACEs reported current use of alcohol (adjusted prevalence ratio [aPR], 5.32) or marijuana (aPR, 5.86), misuse of prescription pain medications (aPR, 8.82), binge drinking (aPR, 7.70), and increased alcohol (aPR, 6.54) or drug (aPR, 7.09) use during the pandemic. DISCUSSION: The individual and combined impact of ACEs and MH on adolescent substance use reinforce the need for trauma-informed care and primary prevention of ACEs to prevent and mitigate poor MH and substance use among adolescents.