Unplanned vs. planned simultaneous alcohol and cannabis use in daily life: What are the motives, contexts, and outcomes?
Authors: Stevens Angela , Gunn Rachel , Boyle Holly , White Helene , Jackson Kristina 
Published: March 2022

Alcohol and cannabis are commonly used by U.S. college students and often used simultaneously (simultaneous alcohol and marijuana [SAM] use). Better understanding situations in which SAM use is planned or unplanned and related consequences of these distinct SAM use events will inform prevention and intervention efforts. We extended previous daily-level research by examining motives and contexts (social, physical) as indicators of unplanned vs. planned SAM use occasions, as well as by parsing specific plans for alcohol use and for cannabis use on SAM use occasions. Specifically, we examined: unplanned alcohol and marijuana (UAM) use, planned mono-substance (either alcohol or cannabis but not both) use (MSU), and planned SAM use. College student SAM users (N=341; 53% women) were recruited from three U.S. universities and completed 56 days of data collection with five repeated surveys each day. Most SAM use occasions were planned (73% of occasions), followed by planned MSU (18%), and by UAM use (10%). Two-level generalized linear mixed-effects models were conducted to account for nesting of occasions within persons and the three-category nominal outcome. All models included age, sex, recruitment site (school), weekend, and other drug use as covariates. At the within-person level, using for social or enhancement reasons was related to higher odds of planned SAM use (vs. UAM use). These reasons for use were also related to planned SAM use when compared to planned MSU, whereas using because it was offered or to cope was related to lower odds of planned SAM use (vs. planned MSU). Using at home or alone was linked to lower odds of planned SAM use (vs. UAM use), and using at a party, friend’s place, with friends, with more intoxicated people, and with more people using cannabis was associated with higher odds of planned SAM use. An identical pattern was found when comparing planned SAM use to planned MSU. When disaggregating “planned MSU” into planned alcohol use-unplanned cannabis use vs. planned cannabis use-unplanned alcohol use, using for social or enhancement reasons was related to higher odds of planned alcohol-only use. Likewise, using at a party, with friends, with strangers/acquaintances, with more intoxicated people, and with more people using cannabis were related to higher odds of planned alcohol-only use. Using at home or alone was linked to lower odds of planned alcohol-only use. Findings suggest that interventions should target days when college students are planning for SAM use. Mobile health interventions could also focus on higher risk motives (e.g., social) and contexts (e.g., party) that were indicators of planned SAM use, as well as target individuals who endorse using substances to cope or because substances were offered, with these latter individuals being at risk for unplanned SAM use when only MSU was originally planned. Specifically, ecological momentary interventions and just-in-time adaptive interventions could send protective behavioral strategies to individuals endorsing intentions for use and high-risk motives or contexts to reduce the heavy alcohol and cannabis consumption that was associated with planned SAM use.