Patterns of substance use on a given day in a national sample of U.S. young adults

Young adulthood constitutes a period of substance use risk and many young adults engage in use of more than one substance. While existing work has examined young adult co-use of substances at the day-level, there has not been a comprehensive investigation of day-level substance use that considers mode and intensity of use in a national sample of U.S. young adults.

Individuals were eligible through participation in the nationally-representative Monitoring the Future study in 12th grade in 2018 and reporting past 30-day drinking in 12th-grade. Respondents completed a 14-day daily study in 2019 (n = 911 individuals; modal age 19). Days on which individuals reported alcohol, cannabis, and/or nicotine/tobacco use (n = 3,086 days and 590 individuals) were examined. Latent class analysis was used to identify patterns of substance use at the day-level with stress, boredom, loneliness, and type of day as covariates.

Six patterns of substance use days were identified: Vaping Nicotine (33.69 %), Cannabis Smoking (23.49 %), Alcohol Only (17.10 %), Cannabis Vaping (11.72 %), Multiple Combustibles (7.28 %), and Multimodal Cannabis (6.72 %) days. Stress and boredom were greater on Multimodal Cannabis days compared to most other substance use days. Alcohol Only days were characterized by lower levels of stress, boredom, and loneliness and a greater probability of being a special occasion or a weekend compared to other substance use days.

This study identified heterogeneous patterns of substance use behaviors among U.S. young adults. Understanding these patterns is important for developing intervention strategies that are responsive to specific substance use on a given day.