Racial and ethnic differences in alcohol, cannabis, and illicit substance use treatment: a systematic review and narrative synthesis of studies done in the USA.

Reports from uncontrolled trials and surveys suggest that there are disparities in substance-use outcomes for minoritised racial and ethnic populations, yet few of these disparities have emerged from randomised clinical trials (RCTs). We conducted a systematic review of RCTs published in English of Black or Latinx adults with any non-nicotine substance use disorder that reported rates of treatment initiation, engagement, or substance-use outcome by race or ethnicity. Study quality was assessed by the Joanna Briggs Institute appraisal tool and a Yale internally validated quality assessment. Of the 5204 studies, 50 RCTs met the inclusion criteria, all done in the USA, 24 compared treatment initiation, engagement, or outcome across races or ethnicities and 26 compared these same factors within a race. Few RCTs have reported outcomes specifically for Black or Latinx populations, with nine reporting significant differences by race or ethnicity. Significant differences were found in all studies that evaluated the baseline differences in social determinants. This Review explains the need for optimisation of RCTs to inform the design, delivery, and dissemination of treatment to historically excluded communities.