Using a Group-Based Trajectory Approach to Assess Risk and Protective Factors of Marijuana Use

Abstract

Marijuana is the most widely used illegal substance in the world, and persistent and frequent use during adolescence has been associated with precocious transitions and deleterious consequences in adulthood. This study used a group-based trajectory approach to analyze panel data collected from 1,725 youth participating in the National Youth Study to describe pathways of marijuana use and to explore protective factors that may reduce the continuation of use. A trajectory approach allowed us to operationalize risk based on prior within-person patterns of self-reported marijuana use. Three trajectory groups of marijuana users were identified: chronic users (17%), rising users (40%), and abstainers (43%). Our results show that some protective factors are significantly associated with decreases in marijuana use for each trajectory group (e.g., parent disapproval and non-using peer associations), but others are significantly associated with decreases in marijuana for a particular trajectory group and not others (e.g., school attachment for chronic marijuana users). The implications of our findings are discussed for the risk and protective factor framework, as well as their importance in a society where opinions of marijuana are currently changing.