There are still many questions about how policy changes to marijuana may impact alcohol use and if increases in marijuana use may decrease alcohol use. The current study attempts to see if marijuana and alcohol use at the same time is associated with complementary or substitution effects among a sample of young adults.

The study included 409 young adult participants that reported engaging in simultaneous alcohol and marijuana (SAM). The methods included a longitudinal study with assessments twice daily for six 14-day periods throughout two years. The assessments included questions about daily substance use patterns along with amount and consequences of alcohol use. The study included 9,641 days across all participants and no alcohol or marijuana use was reported for 39% of the total days. Alcohol was reported on 20%, marijuana on 23%, alcohol and marijuana but not SAM on 6.7%, and SAM on 10.9% of the days.

398 of the participants reported at least one day of alcohol use and 282 reported at least 1 day of SAM. Drinking days had an average of 3.89 drinks and 91% of these days had at least 1 positive consequence and 33% had at least 1 negative consequence. Results showed that days with SAM use had a higher average of drinks consumed than alcohol-only. SAM use on any given day was associated with more positive consequences. There should be more research completed on motivations for SAM use along with any physiological interactions between the two drugs. Interventions provided to young adults could potentially benefit from addressing risk associated with SAM use.

Take Away: The current study looks at marijuana and alcohol use at the same time to see if it is associated with complementary or substitution effects among a sample of young adults. The study included 409 young adults who reported engaging in simultaneous alcohol and marijuana (SAM). The study included 9,641 days across all participants and no alcohol or marijuana use was reported for 39% of the total days. Results showed that days with SAM use had a higher average of drinks consumed than alcohol-only. SAM use on any given day was associated with more positive consequences. Interventions provided to young adults could potentially benefit from addressing risk associated with SAM use.

Lee, C. M., Patrick, M. E., Fleming, C. B., Cadigan, J. M., Abdallah, D. A., Fairlie, A. M., & Larimer, M. E. (2020). 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. Alcoholism: Clinical and Experimental Research, 44(3), 689–696. doi: 10.1111/acer.14279