A Systematic Review of the Unique Prospective Association of Negative Affect Symptoms and Adolescent Substance Use Controlling for Externalizing Symptoms

Introduction. Research has consistently implicated externalizing symptoms, such as aggression and delinquency, as antecedents for substance use among youth. Recently, studies have begun investigating an internalizing pathway to substance use, in which substances are used to reduce distress and negative affect. Evidence for an internalizing pathway to substance use is weaker and less consistent than is the evidence for an externalizing pathway to substance use. These results may be confounded given the co-morbidity of internalizing and externalizing symptoms. Thus, an accurate assessment of the effects of internalizing symptoms on youth substance use must control for the contributions of externalizing symptoms to substance use.

Methods. We conducted a systematic review of the literature to examine the unique prospective relationship between negative affect symptoms (depression, anxiety, and internalizing symptoms more broadly) and subsequent adolescent substance use (alcohol, tobacco, marijuana, illicit drugs, and composite scores of substance use), controlling for externalizing symptoms. Following PRISMA guidelines for systematic reviews, we identified 61 studies that tested this association during adolescence, defined as ages 11 to 19.

Results. Findings suggest no clear relationship between anxiety and substance use or between internalizing symptoms and substance use. A unique relationship between depression and substance use was found, though the finding was inconsistent across substances.

Implications for Prevention and Future Directions. First, given the finding that depression uniquely predicts substance use, strategies to address depression may be an important component of youth substance use prevention programs. Future research should investigate moderators (e.g. age, gender) of this relationship to further elucidate for whom and when depression serves as a unique risk factor for substance use. Doing so would identify vulnerable groups of adolescents, critical times for intervening, and certain contexts in which depression is a heightened risk factor for substance use, all of which would improve the effectiveness of prevention programs that address the internalizing pathway to substance use. Second, results suggest no clear association between anxiety and substance use during adolescence; however, to verify the accuracy of these null findings, future research should utilize more specific measurement to differentiate types of anxiety (e.g. social) and the link between each type of anxiety and subsequent substance use. Finally, no compelling association was found between internalizing symptoms and subsequent substance use. Given the differences between anxiety and depression as predictors of substance use, measures of internalizing symptoms that aggregate the two may be misleading. Future research should limit the use of internalizing symptom measures, or at minimum, make comparisons to disaggregated measures of anxiety and depression.