Simultaneous Alcohol and Cannabis Use Linked to More Alcohol Problems Than Using Them Separately
Using alcohol and cannabis at the same time (with overlapping effects) was associated with significantly more alcohol-related consequences than using them on the same day but at different times.
Quick Facts
What This Study Found
Compared to simultaneous use (overlapping effects), concurrent use on the same day without overlapping effects was associated with 55% lower odds of impaired control, 53% lower odds of social impairment, 59% lower odds of risky use, and 64% lower odds of pharmacological effects. No significant differences were found between simultaneous use days and alcohol-only days.
Key Numbers
116 participants, 28-day assessment period. Concurrent vs. simultaneous use odds ratios: impaired control OR=0.45, social impairment OR=0.47, risky use OR=0.41, pharmacological effects OR=0.36 (all p<0.05).
How They Did This
Ecological momentary assessment study with 116 participants (56% female, mean age 23.2) reporting daily substance use and alcohol-related consequences over 28 days. Preregistered multilevel binomial logistic regression analyses.
Why This Research Matters
As dual use of alcohol and cannabis becomes more common, understanding that the timing of co-use matters for harm risk can inform targeted prevention messaging.
The Bigger Picture
This study shifts the conversation from whether people co-use alcohol and cannabis to how they co-use. The finding that timing matters more than simply whether both substances were used on the same day has practical implications for harm reduction messaging.
What This Study Doesn't Tell Us
Young adult sample (mean age 23.2) may not generalize to older populations. Self-report of overlapping effects is subjective. 28-day window captures only a snapshot. Cannot determine causation from observational daily diary data.
Questions This Raises
- ?Does simultaneous use lead to higher blood alcohol levels, or does cannabis alter the subjective perception of impairment?
- ?Would similar patterns hold in older adults or heavier drinkers?
Trust & Context
- Key Stat:
- Same-day use without overlapping effects had 55-64% lower odds of alcohol-related consequences than simultaneous use
- Evidence Grade:
- Preregistered ecological momentary assessment provides strong within-person data, though the young adult sample and self-report measures limit generalizability.
- Study Age:
- 2025 publication with 28-day daily diary data.
- Original Title:
- Simultaneous alcohol and cannabis use is associated with daily consequences reflective of alcohol use disorder symptoms.
- Published In:
- Drug and alcohol dependence, 276, 112924 (2025)
- Authors:
- Howe, Lindy K(4), Bolts, Olivia L, Metrik, Jane(16), Gunn, Rachel L
- Database ID:
- RTHC-06681
Evidence Hierarchy
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Cite This Study
https://rethinkthc.com/research/RTHC-06681APA
Howe, Lindy K; Bolts, Olivia L; Metrik, Jane; Gunn, Rachel L. (2025). Simultaneous alcohol and cannabis use is associated with daily consequences reflective of alcohol use disorder symptoms.. Drug and alcohol dependence, 276, 112924. https://doi.org/10.1016/j.drugalcdep.2025.112924
MLA
Howe, Lindy K, et al. "Simultaneous alcohol and cannabis use is associated with daily consequences reflective of alcohol use disorder symptoms.." Drug and alcohol dependence, 2025. https://doi.org/10.1016/j.drugalcdep.2025.112924
RethinkTHC
RethinkTHC Research Database. "Simultaneous alcohol and cannabis use is associated with dai..." RTHC-06681. Retrieved from https://rethinkthc.com/research/howe-2025-simultaneous-alcohol-and-cannabis
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.