Daily associations between cannabis use and alcohol use in young adults: the moderating role of self-report and behavioral measures of impulsivity

Although impulsivity has been implicated in cannabis and alcohol use, its role in alcohol and cannabis co-use behavior requires further study. We examined the moderating role of self-report and behavioral measures of impulsivity in the daily-level relationships between cannabis use and both (a) likelihood of same-day alcohol use and (b) the number of drinks consumed on the same day. Young adults (n = 153) completed a 90-day Timeline Follow Back assessing the amount of cannabis smoked (in grams), other forms of cannabis (e.g. oils, edibles), and the number of standard drinks consumed each day. Participants also completed a structured interview of Alcohol and Cannabis Use Disorders (AUD/CUD), and both self-report (UPPS impulsivity scales) and behavioral (behavioral disinhibition and delay discounting) measures of impulsivity. Zero-inflated multilevel modeling revealed that negative urgency, delay discounting, and disinhibition were significant, unique moderators of the daily relationship between cannabis and alcohol consumption, after controlling for AUD/CUD symptoms and other covariates. Specifically, individuals high (but not low) on negative urgency and delay discounting showed a positive association between grams of cannabis used on a given day and same-day number of standard drinks consumed. Contrary to expectations, individuals low on negative urgency and low in disinhibition showed a stronger relationship between grams of cannabis consumed and odds of engaging in any drinking on the same day. Results extend research on moderators of within-person, daily-level associations between cannabis and alcohol use, suggesting that several impulsivity-related constructs may contribute to complementary use of cannabis and alcohol among young adults.