| The purpose of this study is to identify potential risk factors that contribute to pre and post treatment substance use and problem substance use among adolescents participating in a drug and alcohol intervention. Studies indicate depressive symptoms implicate elevated substance use and problem substance use (Stein et al., 2011) however few studies have examined how contextual factors may partially explain the relationship between depressive symptoms, substance use, and problem substance use. Reinforcement ratio or the proportion of behavior allocated toward drug activities relative to non-drug activities is associated with substance use (Murphy, Correia, Colby, & Vuchinich, 2005) and may be one path through which elevated depressive symptoms contribute to substance use and problem substance use at treatment onset. Moreover, I investigated if reinforcement ratio at post treatment mediated the relationship between depressive symptoms at baseline and post treatment problem substance use. While delay reward discounting or the tendency to select smaller and more immediate rewards over larger but delayed rewards is associated with adolescent substance use (Stanger et al., 2011), delay reward discounting may strengthen relationships between depressive symptoms, reinforcement ratio, and substance use. Adolescents (37% female; M = 16.2 yr., SD = 1.2; Black 4.9%, Asian 15.4%, Hispanic 13.0%, Caucasian 55.3%) referred to an 8 week motivational interviewing and coping skills intervention completed measures at pre (N = 119) and post (N = 69) treatment. Results revealed that reinforcement ratio did not mediate the relationship between depressive symptoms and substance use at baseline (95% CI = -.23, 1.46). However, reinforcement ratio did mediate the relationship between depressive symptoms and problem substance use at baseline (95% CI = .12, 1.13). Delay reward discounting did not moderate the relationship between depressive symptoms and reinforcement ratio (beta = -.072, t = -1.79, p = .076, 95% CI -.15, .007) or the relationship between reinforcement ratio and problem substance use. Reinforcement ratio did not prospectively mediate the relationship between baseline depressive symptoms and substance use outcomes. Although limited, findings indicate that interventions should increase the salience of alternative non-drug activities among adolescents presenting with elevated depressive symptoms and problem substance use. |
