“…Six of the 25 selected studies were conducted among primary cocaine users (Black & Rosen, 2011;Brewer, Worhunsky, Carroll, Rounsaville, & Potenza, 2008;Schmitz et al, 2009;Streeter et al, 2008;Washio et al, 2011), three among primary opiate users Passetti et al, 2008Passetti et al, , 2011, three among primary alcohol users Cox et al, 2002;De Wilde et al, 2013), eight among primary nicotine users Janes et al, 2010;Mueller et al, 2009;Sheffer et al, 2012;Waters et al, 2003;Yoon et al, 2007) and two among primary marijuana users (Peters, Petry, Lapaglia, Reynolds, & Carroll, 2013;Stanger et al, 2012). One study examined the relationship between impulsivity and treatment outcomes within a heterogeneous sample of drug users, consisting of cocaine, heroin and marijuana dependent subjects (Carpenter, Schreiber, Church, & McDowell, 2006).…”