In March 2017, Manchin was one of 21 senators to sign a letter led by Ed Markey to Senate Majority Leader Mitch McConnell that noted that 12% of adult Medicaid beneficiaries had some form or a substance abuse disorder and that one third of treatment for opioid and other substance use disorders in the United States is financed through Medicaid, and opined that the American Health Care Act could "very literally translate into a death spiral for those with opioid use disorders" due to the insurance coverage lacking adequate funds for care, often resulting in individuals abandoning substance use disorder treatment.