Polysubstance use has a high prevalence in adolescence and is known to continue into young adulthood. Polysubstance is associated with many negative consequences, such as academic failure, mental health problems, substance use disorder, involvement with the justice system, and lower financial earnings. This study aims to provide a model for using multidimensional growth mixture models (MGMMs) to identify trajectories of polysubstance use in adolescents and young adults. This study also looks at the transitions between conjoint substance use trajectories between adolescence and young adulthood and looks at potential moderators to help promote healthier substance use transitions.
Data for this study was taken from the International Youth Development Study (IYDS). IYDS is a longitudinal cross-national study (USA and Australia) examining substance use and development life course patterns. Participants were first recruited in 2002, with the average age being 13. Participants were re-surveyed at 14 and 15 years old and then again at 31. Demographics such as sex, race, and highest parent education were measured. Suspension and expulsion, partner substance use, college graduate, married, parent, age of full employment, adolescent substance use, and young adulthood substance use were also measured.
The results of this study agreed with pre-existing literature that patterns of substance use in adolescence follow into adulthood and showed a tendency to add substances into adulthood. Having a child was found to be a consistent protective moderator and correlated with transitioning to a low-use class in adulthood. Graduating college was another consistent protective factor found for young adults who were in the low-use and alcohol-dominant classes but not polysubstance use as adolescents. Overall, this study identifies critical transitions in education, family, and work roles as potential protective factors that help inform the timing and focus of targeted interventions.
Takeaway: Key transitions in education, family, and work roles are potential protective factors that help inform the timing and focus of targeted interventions for substance use.