"Across racial and ethnic groups, treatment completion rates were generally highest for people receiving treatment that primarily targeted alcohol abuse, followed by treatment for methamphetamines, and were lowest for treatment for heroin (Exhibit 2). Except for opiates and heroin, where the differences were not significant, Asian Americans were more likely than whites to complete treatment for all substances. Conversely, blacks and Hispanics were significantly less likely than whites to complete treatment for all substances except for opiates. Native Americans had significantly lower completion rates than whites for all substances except for cocaine and methamphetamines.
"Blacks and Hispanics were less likely than whites to complete treatment across all settings, and Asian Americans were more likely (Exhibit 3). The alcohol treatment completion rate was generally higher for people discharged from residential settings, followed by intensive outpatient settings. However, Asian Americans and Hispanics were just as likely to complete nonintensive as intensive outpatient alcohol treatment."
Brendan Saloner and Benjamin Lê Cook, "Blacks And Hispanics Are Less Likely Than Whites To Complete Addiction Treatment, Largely Due To Socioeconomic Factors," Health Affairs, 32, no.1 (2013):135-145 doi: 10.1377/hlthaff.2011.0983, p. 138.