Alcohol and cannabis are frequently used together. Previous research has implicated simultaneous use in higher consumption, increased negative consequences (such as blackouts), and greater impairment in tasks, including driving, compared to using alcohol or cannabis separately. The effects of simultaneous use are complex and variable, however, and depend partly not only on the amount consumed but also the types of products and how they are consumed and combined. This study in Alcoholism: Clinical & Experimental Research is the first to explore distinct combinations of alcohol and cannabis products, and their consequences and consumption, on a given day.
Investigators analyzed survey responses from 274 college students aged 18-24 who reported using alcohol and cannabis with overlapping effects. Each participant’s data included five short surveys a day over 54 days administered via a smartphone application. The surveys covered types of alcohol consumed, forms of cannabis (dry leaf, concentrate, or edible), numbers of drinks and/or cannabis uses, and negative consequences. The researchers focused on four categories of use: leaf and beer (the most prevalent); two cannabis products with two or more alcohol products (potentially the most risky); liquor with two cannabis products; and cannabis concentrate with two or more alcohol products. They used statistical analysis to explore associations between these combinations, negative consequences, and amounts consumed, after accounting for participants’ typical use.
Overall, participants who combined alcohol and cannabis use reported negative consequences (i.e., hangover, nausea/vomiting, injury, driving under the influence, blackout, aggression, or unwanted sex) on one in three study days. When they used only leaf and beer they were unlikely to experience negative consequences, and using two cannabis products with beer did not seem to raise that risk. Negative consequences were most commonly reported on days when multiple alcohol products were involved, even controlling for amount consumed. Liquor was more strongly associated with negative consequences than beer or wine. Not surprisingly, single product combinations aligned with lower consumption. The highest reported consumption was associated with multiple alcohol types and two cannabis products. This effect was linked to mixed drinking, rather than the use of cannabis or any particular alcohol product, though liquor may drive consumption more than beer or wine. Using two cannabis products, and/or using cannabis concentrate in any combination, was associated with greater cannabis consumption.
The findings reinforce harm-reduction recommendations to avoid combining multiple products and to choose products linked with lower risks. The study has several imitations, including the unknown role of cannabis tolerance. The investigators recommend further exploration of multiple aspects of simultaneous use.
Does the combination matter? Examining the influence of alcohol and cannabis product combinations on simultaneous use and consequences in daily life. A. Stevens, E. Aston, R. Gunn, A. Sokolovsky, H. Treloar Padovano, H. White, K. Jackson (pp xxx).