... Of the 20 studies included in this review, half (n = 9) were among clients from opioid use treatment clinics (Carr et al., 2021;Conroy et al., 2009;Derefinko et al., 2019;Gannon et al., 2017;Heffernan et al., 2000;O'Gurek et al., 2021;Sansone et al., 2009;Stein et al., 2017;Winstanley et al., 2020); five studies were conducted among the general population (Evans et al., 2020;Merrick et al., 2020;Tang et al., 2020;Z.Wang et al., 2021;Williams et al., 2020); three studies comprised respondents from student populations (Lei et al., 2018;Onu et al., 2020;Swedo et al., 2020); one study was conducted among biological mothers of neonates diagnosed with neonatal opioid withdrawal syndrome (Beltran-Arzate et al., 2021); and one study was conducted among people involved in the criminal justice system (Eaves et al., 2021). The nine treatment centers in the selected studies also represented different settings: five studies were from urban clinics (Carr et al., 2021;Conroy et al., 2009;Gannon et al., 2017;Heffernan et al., 2000;Stein et al., 2017); two studies were from rural clinics (Derefinko et al., 2019;Winstanley et al., 2020); one study was conducted among homeless people receiving care from a mobile treatment facility (O'Gurek et al., 2021); and one study did not specify the treatment setting (Sansone et al., 2009). One article was a case-control study (Conroy et al., 2009), whereas all other articles (n = 19) were cross-sectional studies, including one mixed method study (Beltran-Arzate et al., 2021). ...