State variations in Medicaid enrollment and utilization of substance use services: Results from a National Longitudinal Study.

Medicaid enrollment varies considerably among states. This study examined the association of Medicaid enrollment with the use of substance health services in the longitudinal National Epidemiologic Survey on Alcohol and Related Conditions of 2001-2005. Instrumental variable methods were used to assess endogeneity of individual-level Medicaid enrollment using state-level data as instruments. Compared to the uninsured, Medicaid covered adults were more likely to use substance use disorder treatment services over the next three years. States that have opted to expand Medicaid enrollment under the Affordable Care Act will likely experience further increases in the use of these service over the coming years.