A Systematic Review of Research on Adolescent Solitary Alcohol and Marijuana Use in the United States.

AIMS: Alcohol use and marijuana use tend to be social activities among adolescents. Some youth use alcohol or marijuana while alone. This article provides a framework for examining the risk factors for and consequences of solitary alcohol and marijuana use, grounded in a motivational model that emphasizes coping with negative emotions. Guided by this framework, we conduct the first systematic review of research on solitary alcohol and marijuana use among middle school- and high school-age adolescents. DESIGN: This review does not include data synthesis; it was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) methodology. PubMed, PsycINFO, and Web of Science were searched. Articles were included if they mention solitary alcohol or marijuana (or illicit drug) use among adolescents, ages 12-18 years. Studies on non-human animals, college students, non-English language publications, and articles exclusively about solitary tobacco or inhalant use were excluded. Overall, 22 articles were selected. SETTING: Only studies conducted in the United States were included. PARTICIPANTS: Studies used representative and convenience samples of both general population and clinical youth. MEASUREMENTS: Self-report questionnaire items to assess alcohol or marijuana use were most common. FINDINGS: Prevalence of adolescent solitary alcohol and marijuana use was relatively high (e.g., 14% lifetime solitary drinking in the general adolescent population), particularly in high-risk subgroups (e.g., 38.8% lifetime solitary drinking in a sample that included clinical youth). Risk factors for solitary alcohol and marijuana use include earlier onset and heavier use, coping motives, negative emotions, and positive expectancies about use. Consequences of solitary alcohol and marijuana use include substance use disorder (SUD) symptoms, diminished academic performance, and perceived health. CONCLUSIONS: Risk factors and consequences reflecting coping motives, negative emotions, and substance use disorders symptoms appear to be associated with solitary alcohol and marijuana use, possibly reflecting attempts to self-medicate or cope with stress.