Cannabis and Alcohol Prepartying Among Young Adults: Daily-Level Associations with Cannabis Intoxication and Simultaneous Alcohol and Cannabis Use.

Lewis M.; Calhoun B.; Litt D.; Greene A. · Journal of studies on alcohol and drugs · 2026

**Background & Methods** This longitudinal study examined cannabis and alcohol prepartying (use before social events) among young adults aged 18-25 using ecological momentary assessment (EMA) over 12 months. Participants completed three-week EMA measurement bursts quarterly, with analyses conducted on 507 participants reporting alcohol use and 238 reporting cannabis use on at least one sampled day. **Key Findings** • Cannabis prepartying occurred on 15.9% of all cannabis use days (affecting 37.4% of cannabis users), while alcohol prepartying occurred on 13.6% of all alcohol use days (39.3% of alcohol users), establishing that prepartying is a common pattern for both substances among young adults. • Cannabis prepartying was positively associated with increased duration of intoxication ("hours high"), higher subjective intoxication ratings, and greater likelihood of simultaneous alcohol and cannabis (SAM) use at both within-person and between-person levels. • Alcohol prepartying demonstrated positive associations with SAM use at the within-person level only; this relationship became non-significant after adjustment for drinks consumed and hours intoxicated, suggesting cannabis prepartying may be a more robust independent predictor of polysubstance use patterns. **Dosage & Administration** Not reported. **Safety & Adverse Effects** Not reported. **Evidence Quality** This study provides valuable longitudinal data using intensive EMA methodology, which captures real-time substance use patterns and reduces recall bias. However, limitations include reliance on self-reported intoxication measures without objective biomarkers, potential non-generalizability due to sample characteristics (young adults only), and lack of information on specific cannabis potency or administration routes. The observational design precludes causal inference regarding prepartying's effects on intoxication outcomes. The between-person associations may reflect unmeasured individual differences rather than causal mechanisms. The study represents moderate-quality evidence suitable for informing public health discussions about polysubstance use contexts among young adults, though further research with biological measures and diverse populations would strengthen conclusions.

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