Examining longitudinal associations between polysubstance use and firearm-related risk behaviors from adolescence into emerging adulthood: a group-based multi-trajectory modeling approach.

INTRODUCTION: Firearm access and associated risk behaviors (i.e., firearm storage and carriage) are established factors that increase the risk of firearm-related injuries. While extant research has demonstrated associations between singular substance use and these risks, little is known regarding the impact of polysubstance use on these outcomes. The present study aims to investigate the relationships between polysubstance use in adolescence and four specific firearm-related risks manifesting in emerging adulthood. METHODS: Ten years of annual data from a cohort of 1,042 adolescents initially aged 13-18 years were analyzed to identify polysubstance use trajectories and their associations with firearm-related behaviors in emerging adulthood. Using group-based multi-trajectory modeling, polysubstance use patterns from adolescence to emerging adulthood were identified. Associations between membership in these trajectory groups and four firearm-related risk factors in emerging adulthood-firearm access, improper storage of firearms and ammunition, and frequent carriage-were assessed using multivariable logistic regression. RESULTS: Five distinct polysubstance risk trajectories were identified. The highest rates of firearm access were observed among Chronic Illicit and Non-Illicit Polysubstance Users. The greatest prevalence of improper firearm storage was exhibited by Alcohol Ascenders and Chronic Non-Illicit Users. Additionally, significantly higher odds of engaging in frequent firearm carrying were found for all polysubstance use groups compared to Mild Alcohol Users, with the exception of Chronic Illicit Users. No significant associations were observed for improper ammunition storage across groups. CONCLUSION: This study is among the first to identify specific associations between firearm-related risk behaviors and distinct polysubstance use trajectories. The findings provide novel insights for developing targeted interventions to mitigate firearm risks in polysubstance-using individuals transitioning from adolescence to young adulthood.