Does Simultaneous Use of Marijuana Affect Alcohol Intake and Consequences Among Young Adults?

Newswise — Simultaneous use of alcohol and marijuana (SAM) is common among young people, and is sometimes a deliberate choice to enhance the effects of intoxication. However, compared with alcohol use alone, SAM has been linked to a greater risk of interpersonal problems, physical and mental health issues, and road accidents. Despite this, there has been little research at the occasion level – for example, it is not known if individuals who engage in SAM drink more (or less) alcohol on the occasions when they also use marijuana, and experience more (or fewer) alcohol-related consequences, than on alcohol-only days. Researchers in Seattle and Minneapolis have conducted a new study, published in the journal Alcoholism: Clinical and Experimental Research, to evaluate these aspects, by conducting multiple daily assessments of alcohol and SAM use among the same individuals over time. The study took place in and around Seattle in Washington state, where non-medical marijuana use is legal for those over 21 years of age.  

Around four hundred SAM users aged 18 to 25 years took part, by completing two 14-day bursts of daily surveys (28 surveys in total), 4 months apart, in which they reported on their previous day’s alcohol and marijauana use (or lack of) and any alcohol-related consequences experienced. Participants could select from a list of fifteen negative consequences (such as had hangover, passed out, blacked out, vomited, got into a fight, damaged property, felt confused, etc), and of six consequences that they perceived as positive, such as feeling relaxed or in a better mood. This enabled analysis of the motivating factors that may reinforce SAM use, as well as of the risks. The total numbers of positive and negative consequences experienced by an individual on each alcohol-only or SAM occasion were calculated.  

The researchers found that on days when the young adults used alcohol and marijuana simultaneously, they consumed more drinks and experienced more alcohol-related consequences (both negative and positive) than on alcohol-only days. The increase in consequences, particularly negative consequences, was partially explained by the greater quantity of alcohol consumed on SAM days; for perceived positive consequences, the effect of SAM use was over and above that accounted for by alcohol intake.

Overall the data show a strong complementary effect of marijuana on alcohol use, and enhance understanding of young people’s motivation for engaging in high-risk SAM behavior. The findings suggest that targeted alcohol interventions could benefit from addressing the risks associated with SAM use, including greater alcohol intake. A motivation-based approach to intervention, balancing the perceived positive consequences against the negative, may be of value.

A Daily Study Comparing Alcohol-Related Positive and Negative Consequences for Days with Only Alcohol Use versus Days with Simultaneous Alcohol and Marijuana Use in a Community Sample of Young Adults. C.M. Lee, M.E. Patrick, C.B. Fleming, J.M. Cadigan, D.A. Abdallah, A.M. Fairlie, M.E. Larimer (pages xxx).

ACER-19-4116.R1