Making Decisions with Trees: Examining Marijuana Outcomes among College Students using Recursive Partitioning.

Exploratory analyses were used to identify a unique constellations of variables that are associated with marijuana use outcomes among college students. We used recursive partitioning to examine over 100 putative antecedents of lifetime marijuana user status, past-month marijuana user status, and negative marijuana-related consequences. Participants (N=8141) completed measures online across 11 sites in the USA. Norms (descriptive, injunctive, and internalized norms) and marijuana identity best distinguished marijuana users from non-users (i.e., lifetime/past month), whereas marijuana use frequency, use of protective behavioral strategies, and positive/negative urgency best distinguished the degree to which users reported negative consequences. Our results demonstrate that tree-based modeling is a useful methodological tool in the selection of targets for future clinical research. Additional research is needed to determine if these factors are causal antecedents, rather than consequences or epiphenomena. We hope this large sample study provides the impetus to develop intervention strategies targeting these factors.