Key subgroup differences in age-related change from 18 to 55 in alcohol and marijuana use: U.S. national data (2021)

OBJECTIVE: This study examined age-related change in alcohol use, marijuana use, and the association between the two, from ages 18 to 55, in a national longitudinal sample.
METHOD: Data were from national Monitoring the Future study participants (N = 11,888) who were high school seniors in 1976-1980 and were eligible to respond to the age 55 survey in 2013-2017. Time-varying effect modeling was used to model past-30-day prevalence and associations between alcohol and marijuana across ages 18-55, overall and by sex, race/ethnicity, and college attendance.
RESULTS: Marijuana prevalence peaked at age 18 and was lowest in the late 40s; alcohol prevalence peaked at age 22 and was lowest in the early 40s. Associations between alcohol and marijuana use were strongest at age 18. Significant differences were observed by sex, race/ethnicity, and college attendance (e.g., women's use was lower and decreased faster in the late 30s than men's; White respondents' alcohol and marijuana use were higher and peaked before Black respondents'; compared with non-attenders, college attenders' use was higher for alcohol but lower for marijuana). The alcohol and marijuana use association was strongest at ages 18-20 for most subgroups, except Black respondents, for whom the association was strongest at age 30.
CONCLUSIONS: Longitudinal data showed patterns of alcohol and marijuana use across adulthood. Such patterns highlight sociodemographic risk factors across the life span, ages that should be targeted for clinician awareness and intervention efforts, and populations at particular risk of harm from alcohol and marijuana co-use during adulthood.