In daily-level data from Washington State, recreational cannabis users showed a complementary pattern (more drinking on cannabis days), while medical cannabis users showed a substitution pattern (less drinking on cannabis days).
Alcohol and cannabis researchers, public health policymakers, and anyone interested in how legalization affects drinking patterns.
What the researchers found
At the daily level, recreational cannabis users drank 37% more alcohol on cannabis-use days (IRR = 1.37). Medical cannabis users showed the opposite — a 43% reduction (IRR = 0.57 interaction), suggesting substitution. This indicates the relationship between cannabis and alcohol depends on the type of cannabis user.
Why it matters
Whether cannabis replaces or adds to alcohol use has major public health implications. This study shows it depends on why people use cannabis — recreational users combine them, while medical users may genuinely substitute.
The numbers in context
259 respondents, 440 person-waves, 3,051 daily observations. Recreational users: IRR = 1.37 (95% CI: 1.05-1.79) on cannabis days. Medical recommendation interaction: IRR = 0.57 (95% CI: 0.34-0.96).
How the study worked
Three-level negative binomial models analyzing daily alcohol and cannabis use data from 259 co-users across 4 waves of the Washington Panel Survey (2014-2016), with 3,051 daily observations.
What this study cannot tell us
Washington State sample during early legalization may not represent current or other markets. Self-reported daily use. Medical recommendation doesn't necessarily mean using for medical purposes.
How to read the evidence
Innovative within-person daily-level analysis resolving a long-standing research question, though limited by single state and early legalization period.
When this study was published
Recent analysis of 2014-2016 daily-level data from Washington, one of the first states to legalize recreational cannabis.
The bigger picture
The substitute-vs-complement debate has been inconclusive because researchers haven't distinguished between recreational and medical users. This daily-level analysis resolves the contradiction — both patterns exist in different populations.
Questions still open
- Would medical cannabis programs reduce alcohol-related harm at the population level? Could recreational legalization increase alcohol-related problems through complementary use?
Common questions
Does cannabis replace alcohol?
Why does user type matter?
Read the original research
Does cannabis substitute or complement alcohol after recreational cannabis legalization in the Washington State? A three-level mixed-effects modeling.
Addictive behaviors, 162, 108218
Citation
Zhu, Yachen; Trangenstein, Pamela J; Kerr, William C. (2025). Does cannabis substitute or complement alcohol after recreational cannabis legalization in the Washington State? A three-level mixed-effects modeling.. Addictive behaviors, 162, 108218. https://doi.org/10.1016/j.addbeh.2024.108218