Adolescent substance use trajectories in relation to internalizing problems in young adulthood: The role of friendship quality

Abstract

The aim of this longitudinal study was to examine whether adolescents’ substance use trajectories from early adolescence to young adulthood were related to internalizing problems during the transition into young adulthood. Friendship quality was examined as a moderator. Seven annual measurements from the Research on Adolescent Development And Relationships project (RADAR, N=497) were used. Self-reports of past year cannabis and hard drug use revealed five trajectories: ‘Early accelerating’, ‘Late accelerating’, ‘Decreasing’, ‘Rare’ and ‘No use’. Trajectory membership was unrelated to later internalizing problems. Only non-users were emotionally affected by friendship quality, for better and for worse. Since substance use does not jeopardize emotional wellbeing, interventions should focus on other detrimental processes in peer groups threatening the emotional wellbeing of adolescents.