The role of alcohol and cannabis co‐use in drinking rate and its impact on consequences

Abstract

Background The impact of alcohol and cannabis co‐use on college student drinking and related outcomes is complex. Specific characteristics or patterns of co‐use events beyond drinking quantity may be important to the experience of consequences. The present study used repeated daily surveys to examine the association between co‐use (versus use of alcohol only) and drinking rate on negative consequences. Methods The sample included 318 college students (Mage = 19.8, 47% female, 76% non‐Hispanic White) who were co‐users of alcohol and cannabis, recruited from three U.S. college campuses. Participants completed 56 days of data collection (number of drinking days ranged from 1 to 38). Two measures of drinking rate were examined: (1) daily rate (number of drinks divided by number of hours spent drinking per day); and (2) peak hour rate (maximum number of drinks consumed in a single hour) to account for anomalous drinking days of long duration. Generalized linear mixed models examined: (1) associations of co‐use with peak hour rate (model 1a) and daily rate (model 1b); (2) associations of peak hour rate (model 2a) and daily rate (model 2b) with experiencing any negative consequence; and (3) interactions of co‐use with peak hour rate (model 3a) and daily rate (model 3b) on experiencing a consequence. Results Co‐use was positively associated with peak hour rate but not daily rate. Both peak hour and daily rate positively predicted likelihood of experiencing a negative consequence. The interaction of both peak hour and daily rate by co‐use was significant such that the association of rate with experiencing a consequence was stronger on alcohol‐only days compared to co‐use days. Conclusions Daily drinking rate and peak hour drinking rate are unique and should be considered when discussing drinking patterns. Both predict negative consequences and may be important aspects of interventions for negative drinking‐related outcomes among college students.

Interactive effects of alcohol and cannabis quantities in the prediction of same‐day negative consequences among young adults

“…These findings are similar to the results of two previous studies that examined how cannabis use moderates the day‐level association between indices of alcohol consumption (i.e., number of drinks, rate of consumption) and negative alcohol consequences, which found that cannabis use (vs. no use) weakened this within‐person association (Gunn et al., 2022; Sokolovsky et al., 2020). However, the nature of the moderating effect we observed differed from these prior studies when comparing the simple slopes.…”

“…This might reflect the tendency for heavy drinking to be risky in general, and so adding cannabis to a heavy drinking episode may not confer much additional risk; in contrast, the addition of cannabis to a light drinking episode may escalate intoxication to levels that confer greater risk for harms than would be expected from light drinking alone. However, contrary to the findings of Boyle et al, other ILD studies have found that the quantity of alcohol consumed (Sokolovsky et al, 2020) and rate of alcohol consumption (Gunn et al, 2022) were weaker predictors of negative consequences on simultaneous use days relative to alcohol-only days. This suggests that perhaps cannabis can have quantities.…”

“…Sokolovsky et al (2020) andGunn et al (2022) both found that negative consequences did not increase as much as a function of heavier or faster drinking on days when alcohol was combined with cannabis relative to days when alcohol was used alone, we found that negative consequences did not decrease as much as a function of lighter drinking on simultaneous use days when a larger amount of cannabis flower was used relative to days when a smaller amount of cannabis was used. In other words, we found that the decline in negative consequences associated with relatively lighter alcohol consumption was less steep on days when relatively larger amounts of cannabis flower were used.F I G U R E 1 Interaction between quantities of alcohol (standard drinks) and cannabis flower (grams) consumed in the prediction of negative consequences on simultaneous use days involving cannabis flower use.…”

High‐intensity drinking and hours spent drinking

“…In our study, HID days were associated with the quickest pace of drinking, as well as a greater number of consequences. Other work also highlights the relationship between quicker rates of drinking and negative alcohol consequences, even when controlling for quantity of drinks consumed (Carpenter & Merrill, 2021; Gunn et al, 2022; Kuntsche et al, 2015). Although our measurement of HID is focused on the number of drinks consumed, it still evidenced the fastest pace and greatest number of consequences compared with other drinking levels.…”

“…Similarly, Carpenter and Merrill (2021) found that the amount of alcohol consumed and the rate of consumption were both associated with a greater likelihood of experiencing a negative consequence (e.g., blackout and hangover) the next morning. Finally, Gunn et al (2022) found that both consuming more drinks during the peak hour of drinking and faster daily rate of drinking were associated with experiencing negative consequences, even when controlling for the amount of alcohol consumed. Taken together, these findings suggest that accounting for the rate of drinking is important when assessing risk for negative alcohol consequences.…”