Nonmonotonic Associations Between Cannabis Use Frequency and Alcohol Use in a Statewide Sample of Young Adults From Washington State.

INTRODUCTION

Young adult cannabis use is positively associated with alcohol use, but some research suggests that individuals who use cannabis daily or near daily drink less than individuals who use cannabis less frequently. This study delineated nonmonotonic associations between cannabis use frequency and alcohol use among young adults in Washington state.

METHODS

Data were from young adults recruited into the Washington Young Adult Health Study between 2015 and 2022 (N=15,217; aged 18-25 years at recruitment). After baseline, participants completed annual follow-up surveys, providing 43,423 observations covering ages 18-33 years. In multilevel models, past-month any heavy episodic drinking and days of alcohol use were regressed on concurrent past-month cannabis use days, which was indicator coded into 8 categories ranging from no use to daily use. Data were analyzed in the summer of 2025.

RESULTS

Both heavy episodic drinking prevalence and alcohol use days were lowest when no cannabis use was reported and were positively associated with cannabis use across cannabis use frequency between none and 5-9 days. Both measures of alcohol use were lower at upper frequencies of cannabis use such that daily or near daily cannabis use (≥25 days) was associated with less drinking than occasional cannabis use (5-24 days). Nonmonotonic associations were present across age groups (18-20, 21-25, ≥26 years).

CONCLUSIONS

Nonmonotonic associations between cannabis and alcohol use may be consistent with substance use specialization among some young adults who use cannabis or alcohol frequently.