Is it Selection or Socialization? Disentangling Peer Influences on Heavy Drinking and Marijuana Use Among Adolescents...

This study attempted to disentangle the effects of peer selection and socialization on heavy drinking and marijuana use among adolescents whose parents received 2 distinct brief interventions (BIs). It also examined whether the two BI models-Family Check-Up and Psychoeducation-had differential effects on peer processes. Parents were randomized to BI conditions and their adolescents (61% male, age 12-19 years) completed self-report measures of days of heavy drinking, days of marijuana use, and perceived peer substance involvement at baseline, 6 months, and 12 months. Separate cross-lagged panel models revealed evidence of selection and socialization for both heavy drinking and marijuana over the first 6 months and evidence of only selection over the subsequent 6 months. Consistent with prior studies, a less robust pattern of peer processes was found when simultaneously controlling for both heavy drinking and marijuana. Results highlight the need to examine multiple substances simultaneously and suggest that the BIs may have had protective effects on peer influences over time.