Alcohol and Cannabis Use Milestones in Diverse Urban Adolescents: Associations with Demographics, Parental Rule Setting, Sibling and Peer Deviancy, and Outcome Expectancies.

Objective: Alcohol and cannabis use progression milestones in adolescence (such as ages at first use, first intoxication and at onset of regular use) may inform the development of alcohol and cannabis use disorders. Although parent, sibling, and peer behavior and alcohol-related cognitions have been shown to be associated with alcohol milestone attainment, findings have been mixed; further, those factors' associations with cannabis use milestones are unknown. This study examined whether progression through such milestones differed as a function of perceived peer/sibling deviancy, parental rule-setting, and substance use outcome expectancies in a racially diverse adolescent sample.Methods: Data were drawn from a two-wave longitudinal health survey study of 9-11th graders (n = 355 for the current analyses; Mage=15.94 [SD = 1.07]; 44% male; 43% Black; 22% White; 18% Asian; 17% Multiracial; 10% Hispanic/Latinx ethnicity) at an urban high school. A series of logistic and proportional hazards regressions examined associations of peer/sibling deviancy, parental rule-setting, and outcome expectancies with age and attainment of alcohol/cannabis use milestones.Results: For both alcohol and cannabis, greater peer deviancy and positive expectancies were associated with higher odds of milestone attainment, while negative expectancies were associated with slower progression through milestones. For cannabis, but not alcohol, greater perceived sibling deviancy was positively associated with milestone attainment, while negative expectancies were associated with lower odds of milestone attainment.Conclusions: Perceived deviant behavior by peers and siblings, in addition to adolescents' expectancies for either alcohol or cannabis use, is associated with attainment and progression through key adolescent substance use milestones.