Marijuana Legalization and Youth Marijuana, Alcohol, and Cigarette Use and Norms

INTRODUCTION Rates of adolescent substance use have decreased in recent years. Knowing whether nonmedical marijuana legalization for adults is linked to increases or slows desirable decreases in marijuana and other drug use or pro-marijuana attitudes among teens is of critical interest to inform policy and promote public health. This study tests whether nonmedical marijuana legalization predicts a higher likelihood of teen marijuana, alcohol, or cigarette use or lower perceived harm from marijuana use in a longitudinal sample of youth aged 10-20 years. METHODS Data were drawn from the Seattle Social Development Project-The Intergenerational Project, an accelerated longitudinal study of youth followed both before (2002-2011) and after nonmedical marijuana legalization (2015-2018). Analyses included 281 youth surveyed up to 10 times and living in a state with nonmedical marijuana legalization between 2015 and 2018 (51% female; 33% white, 17% African American, 10% Asian/Pacific Islander, and 40% mixed race or other). RESULTS Multilevel modeling in 2019 showed that nonmedical marijuana legalization predicted a higher likelihood of self-reported past-year marijuana (AOR=6.85, p=0.001) and alcohol use (AOR 3.38, p=0.034) among youth when controlling birth cohort, sex, race, and parent education. Nonmedical marijuana legalization was not significantly related to past-year cigarette use (AOR=2.43, p=0.279) or low perceived harm from marijuana use (AOR=1.50, p=0.236) across youth aged 10-20 years. CONCLUSIONS It is important to consider recent broad declines in youth substance use when evaluating the impact of nonmedical marijuana legalization. States that legalize nonmedical marijuana for adults should increase resources for the prevention of underage marijuana and alcohol use.