LAUSR

AIMS In the last decade the relatively lower levels of marijuana use for black relative to non-black high school seniors has grown smaller and disappeared, drawing to a close a unique disparity that actually favored a disadvantaged group for at least thirty years. In this study we test trends in cigarette smoking and religiosity as possible explanations for this closing disparity. The study also examines whether increasing marijuana levels for black adolescents is better characterized as a cohort effect or an historical period effect. DESIGN Analyses use relative risk regression and focus on data from yearly, cross-sectional surveys from the time period 2008-2017. SETTING AND PARTICIPANTS Data comes from the nationally-representative Monitoring the Future survey, which conducts in-school surveys of secondary school students. The analysis uses data from 114,552 high school seniors (in 12th grade), 123,594 in 10th grade, and 136,741 in 8th grade. FINDINGS Past 12-month marijuana prevalence significantly increased for black as compared to non-black adolescents from 2008 to 2017 in 12th grade, 10th grade, and 8th grade. The increase attenuated by more than half and was not statistically significant after adjusting for cigarette smoking. In contrast, the increase was little changed after adjusting adolescent levels of religiosity. The increase is better characterized as a cohort effect than a period effect. CONCLUSIONS These results support the increase in marijuana use for black relative to non-black adolescents as an unexpected consequence of the great decline in adolescent cigarette smoking, which has occurred slower for black adolescents.