“…Marijuana and cigarettes, two commonly used substances among adolescents and young adults (Johnston et al, 2014) are often used concurrently (Kandel & Yamaguchi, 1993; Patton et al, 2006; Prince van Leeuwen et al, 2013; Rigotti et al, 2000; Silins et al, 2013), leading to escalating use and severity of dependence (Degenhardt et al, 2001; Kandel & Yamaguchi, 1993; Korhonen et al, 2008; Lynskey et al, 1998; Mathers et al, 2006; Patton et al, 2006). These substances are each associated with negative outcomes, including increased risk of depression (Brook et al, 2012; CDC, 2012, 2013; Cuijpers et al, 2007; Degenhardt et al, 2003; Hayatbakhsh et al, 2007; Klungsoyr et al, 2006; Mathers et al, 2006; Pedersen & von Soest, 2009; van Laar et al, 2007), especially if use is initiated in adolescence (Silins et al, 2014); but these relationships may differ by gender.…”