Cost Offsets of Treatment for Serious Mental Illness and Substance Use Disorder.

Objective: The authors examined whether timely treatment for serious mental illness and substance use disorder reduces overall health care costs in a 3-year period.

Methods: Claims data from the IBM MarketScan Research Databases (2010-2017) were analyzed. The population studied included 2,997 Medicaid enrollees and 35,805 commercial insurance enrollees ages 18-64 years with an index event for a serious mental illness and 2,315 Medicaid enrollees and 28,419 commercial insurance enrollees with an index event for a substance use disorder. Health care costs in the 3 years after an index event were calculated for enrollees who received care that met a minimum threshold for treatment and for those who did not receive such care. The Toolkit for Weighting and Analysis of Nonequivalent Groups was used to control for statistically significant differences in pretreatment characteristics between the groups.

Results: All health care spending for enrollees who were engaged in behavioral health treatment for substance use disorder or a serious mental illness increased from year 0 to year 1 but decreased faster than the spending of enrollees who were not engaged in treatment, with larger trends for those engaged in substance use disorder treatment. Expenses for inpatient and emergency department care decreased over the 3 follow-up years; however, spending on outpatient services was significantly higher in all 3 follow-up years for those engaged in treatment.

Conclusions: Health care delivery and payment models that improve access to behavioral health treatment may reduce emergency department, inpatient, and overall health care costs for particular subpopulations.