Public Release: 

Medicaid expansion states see rise in coverage for low income adults with substance use disorders

No increase reported in substance use treatment

Columbia University's Mailman School of Public Health

August 14, 2018 -- The percentage of low-income Americans with substance use disorders who were uninsured declined more sharply in states that chose to expand Medicaid under the Affordable Care Act versus states that did not, according to a new study at Columbia University's Mailman School of Public Health and Columbia University Irving Medical Center. The results are published online in the journal Health Affairs.

The percentage of low-income residents with substance use disorders without coverage decreased from 34 percent in 2013 to 20 percent in 2015 within states that had implemented Medicaid expansion - or expansion states -- compared to 45 percent to 39 percent in non-expansion states. Yet while more in the group were covered in Medicaid expansion states than those living elsewhere, Medicaid expansion states saw no corresponding increase in substance use treatment.

"Despite an increase in health insurance in Medicaid expansion states, the proportion of the adults who received treatment did not increase," says Mark Olfson, MD, MPH, professor of Epidemiology at Columbia's Mailman School of Public Health and professor of Psychiatry at Columbia University Vagelos College of Physicians and Surgeons. "This may be because serious substance use problems tend to interfere with the ability to recognize the severity of drug use or perceive a need for treatment. Although insurance coverage may be necessary, it is often not sufficient for people to seek help for their substance use problems."

The researchers used data for the years 2008 to 2015 from the National Survey on Drug Use and Health to assess changes in Medicaid coverage and substance use disorder treatment among low income adults in states that did and did not expand Medicaid eligibility. They focused on four substance use disorders: alcohol, cannabis, heroin, and cocaine.

Before the 2014 Affordable Care Act Medicaid expansion, most low-income people in need of substance use disorder treatment were ineligible for Medicaid. By the end of 2014, however, 26 states and the District of Columbia had expanded Medicaid eligibility to include nearly all low-income residents with household incomes up to 138 percent of the federal poverty level. Because low-income people are at increased risk for substance use disorders and for not having health insurance, the Medicaid expansion provision has been widely viewed as an important potential means of increasing access to substance use disorder treatment, under the presumption that there is pent-up demand for it.

"In light of persistently high levels of untreated substance use disorders, it will be important to track national trends in treatment patterns and outcomes, as clinical and public policy experience with the Medicaid expansion population matures over the next several years," says Olfson.


Co-authors include Christine Mauro and Melanie Wall, Columbia Mailman School; and Colleen Barry and Ramin Mojtabai, Johns Hopkins Bloomberg School of Public Health. The study was supported by the National Institute on Drug Abuse (DA039137).

Columbia University's Mailman School of Public Health

Founded in 1922, Columbia University's Mailman School of Public Health pursues an agenda of research, education, and service to address the critical and complex public health issues affecting New Yorkers, the nation and the world. The Mailman School is the third largest recipient of NIH grants among schools of public health. Its over 450 multi-disciplinary faculty members work in more than 100 countries around the world, addressing such issues as preventing infectious and chronic diseases, environmental health, maternal and child health, health policy, climate change & health, and public health preparedness. It is a leader in public health education with over 1,300 graduate students from more than 40 nations pursuing a variety of master's and doctoral degree programs. The Mailman School is also home to numerous world-renowned research centers including ICAP and the Center for Infection and Immunity. For more information, please visit

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