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UBC Theses and Dissertations

The impact of cannabis-alcohol co-use on drink consumption : timing is key Rootman, Joseph Marc


Heavy episodic drinking (HED) of alcohol is a dangerous and highly prevalent behaviour among college students, and the risks associated with HED increase dramatically with each drink consumed. Past research has been inconsistent in determining if the co-use of cannabis and alcohol is more harmful than alcohol use (AU) on its own, or if co-use impacts drink consumption. Importantly, if co-use is not more harmful than AU on its own, and co-use is associated with reduced drink consumption, then it follows that co-use reduces the harm associated with HED by way of minimizing drink consumption. The present study used daily diary methods to explore the impact of co-use on drink consumption and built on past research through the consideration of 3 previously unexplored factors: 1) temporal precedence of cannabis use (CU) to AU, 2) intention to substitute CU for AU and 3) quantity of CU consumed in a given AU session. 146 college students completed 3 surveys daily and reported on characteristics of AU sessions. Multilevel models were used to assess within- and between-person variations in drink consumption. Results indicated that CU before or during an AU event was associated with lower levels of drink consumption relative to AU events where CU occurred only after an AU event. Additionally, although co-use was not associated with drink consumption levels, co-use before/during AU was associated with lower levels of drink consumption relative to drinking events wherein CU occurs only after AU or not at all. These findings extend past research by highlighting the importance of temporal precedence in the evaluation of the relationship between co-use and drink consumption, and suggest that CU before or during an AU event may reduce harm by way of reducing drink consumption. Agencies that distribute harm reduction guidelines, as-well as government and private organizations, can incorporate these findings into practice by moving away from overarching recommendations or prohibitions against co-use.

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