Many Factors Predict Teens Trying Cannabis, But Only a Few Drive Escalation to Weekly Use

Random Survival Forest predicted first cannabis onset (C-index 0.68) and weekly onset (C-index 0.69). First use was predicted by 13 factors across 6 domains (biobehavior, cognition, family, peer, neighborhood, legal). Weekly use required only 4 factors, with 3 shared with first use: cannabis outlet density, access to alcohol at home, and positive social expectations about alcohol.

Data-driven analysis of 151 measurements spanning 7 domains from the NCANDA cohort (450 cannabis-naïve youth, ages 12–21, followed 8 years). Random Survival Forest modeled age of first onset (292 transitioned) and weekly use onset (163 transitioned). Factors from individual, microsystem, and exosystem levels assessed.

The distinction between first use (many factors) and escalation to weekly use (few factors) is crucial for prevention. First use may be hard to prevent because it's influenced by many small factors, but escalation to habitual use may be preventable by targeting just a few key environmental factors.

The finding that cannabis outlet density and home alcohol access drive escalation to weekly use suggests environmental interventions — like zoning regulations and parental alcohol management — may be more effective at preventing habitual cannabis use than individual-level interventions.

NCANDA cohort may not represent all U.S. youth. C-index of ~0.68 indicates moderate prediction. 8-year follow-up may not capture all initiators. Some domains (brain MRI) had limited predictive contribution. Legal environment may have changed since data collection.