A Longitudinal Study of Alcohol and Cannabis Use in Young Adulthood: Exploring Racial and Ethnic Differences in the Effects of Peer and Parental Influences From Middle Adolescence

Objective: This study assessed how changes from middle adolescence to young adulthood in peer and parental influences relate to frequency of alcohol and cannabis use in young adulthood and evaluated the differences between three racial/ethnic groups. Method: The analytic sample (n = 2,808; 52.9% female; 54% Hispanic, 22.9% White, 23.1% Asian/Pacific Islander) was derived from a longitudinal cohort initially recruited from 16 middle schools in Southern California who completed annual surveys. Data were collected across six waves beginning in Spring 2013 (mean age = 16.2) through Spring 2019 (mean age = 21.6). Results: Multigroup latent growth models revealed consistent increases during adolescence and young adulthood in perceived peer and parental approval of alcohol and cannabis and in the amount of time spent around peers who used these substances. After we controlled for prior use, these increases related to alcohol and cannabis use at age 21, with few exceptions. The time spent around peers most strongly influenced later cannabis use for Hispanic young adults, whereas the influence of peer approval on later alcohol and cannabis use, and parental approval on later alcohol use, was strongest among White young adults. Conclusions: The frequency of alcohol and cannabis use in young adulthood was shaped, in part, from increases in direct and indirect peer influence and perceived parental approval of substance use across two important developmental periods. The findings highlight the importance of early and sustained intervention efforts targeting these social influences, especially among White adolescents, which may potentially decrease alcohol and cannabis use as youth enter young adulthood