In 2015, 20.8 million people aged 12 years or older (7.8 percent of the United States population) had a substance use disorder (SUD) in the previous year. Approximately 75 percent of this group, or 15.7 million Americans, had an alcohol use disorder, 2.0 million had a prescription opioid use disorder (OUD), and about 0.6 million had a heroin use disorder. Even though evidence-based SUD treatments are effective, rates of treatment receipt are quite low. Only about 48 percent of patients who enter SUD treatment actually complete it. One measure of treatment receipt is the Initiation and...