The impact of Medicaid expansion in 2014 on prescription second-generation antidepressant utilization in Washington State: An interrupted time series analysis

Abstract: Background Depressive disorders, specifically major depressive disorder (MDD), is predicted to become the leading cause of disease burden worldwide by 2030. In the United States, MDD is already the leading cause of disability. Yet, less than 50 percent of US adults diagnosed with a mental disorder seek treatment, often due to lack of health coverage or affordability. In 2014, the Affordable Care Act expanded Medicaid eligibility in select states to extend health and medication coverage to previously uninsured Americans. Medicaid expansion has been shown to increase medication use in expansion states, however, few studies have examined how Medicaid expansion has impacted a specific drug class such as second-generation antidepressants. This study looked at the impact of Medicaid expansion on antidepressant utilization in Washington State, a state that participated in expansion and reports one of the highest rates of depression in the U.S. Objective The objective of this study was to evaluate second-generation antidepressant utilization measured by number of prescriptions filled before and after Medicaid expansion in 2014, while also accounting for known increases in Medicaid enrollment. Methods An interrupted time series analysis was conducted using Medicaid state drug utilization data from 2011 to 2016. The primary outcome was changes in quarterly antidepressant use before and after Medicaid expansion in Washington. The secondary outcome was per-member-per-quarter (PMPQ) antidepressant utilization before and after expansion, which accounted for the increase in Medicaid enrollees. Results Washington experienced a significant trend increase in antidepressant utilization after Medicaid expansion. Specifically, total utilization increased by 14,912 prescriptions per quarter after expansion (p < .001) and PMPQ utilization increased by .008 (p < .05) after expansion compared to the pre-expansion utilization trend. Conclusions Study results suggest that prescription second-generation antidepressant use increased in Washington after full Medicaid expansion in 2014, partly due to the influx of new enrollees.