Did the dependent coverage expansion increase risky substance use among young adults?

•Literature suggests that health insurance may increase risky substance use.•A provision of the Affordable Care Act (ACA) increased coverage among young adults.•We tested the impact of this ACA provision on risky substance use.•Evidence suggests that coverage did not result in an increase in substance use. The dependent coverage expansion (DCE) enacted through the Affordable Care Act increased health insurance coverage among young adults. Increasing insurance coverage in this age group has the potential for unintended consequences on risky substance use. Repeated cross-sectional surveys were used to compare change in substance use during the period the DCE was implemented in the 19–25year old target age group (Pre-DCE n=15,772, Post-DCE n=22,719) with contemporaneous change in a slightly older age group that was not targeted by the policy (Pre-DCE=19,851, Post-DCE n=28,157). Outcomes include 11 measures of alcohol, illicit drug and cigarette use. Statistical controls were included for demographic and socioeconomic factors and for early initiation of substance use to adjust for historical trends in developmental trajectories. Risky substance use decreased in young adults relative to the older age group over the period that the DCE was implemented. However, statistical adjustment for initiation of substance use prior to age 18, which is prior to exposure to the DCE, accounted for the differences between the age groups. In adjusted models, associations between the DCE and substance use outcomes range from 0.96 to 1.08 with p-values ranging from 0.330 to 0.963. Historical trends in initiation of substance use prior to age 18, not the DCE, account for change in risky substance use among 19–25year olds relative to 26–34year olds. The evidence does not support the suggestion that health insurance coverage would increase risky substance use among young adults.