Young adults who co-used cannabis and alcohol reported greater intoxication than with either substance alone, and those who felt more intoxicated during co-use were more likely to increase hazardous cannabis use over the next year.
Young adults who use both substances, harm reduction counselors, college health providers
Co-use within 30 minutes produced the greatest intoxication amplification
What the researchers found
Co-use of cannabis and alcohol was associated with greater momentary intoxication compared to either substance alone, and greater stimulation and bad effects compared to cannabis alone. Using both within 30 minutes produced the strongest effects. Individuals who became more intoxicated during co-use had greater risk of increasingly hazardous cannabis use at 6 and 12 months.
Why it matters
Cannabis-alcohol co-use is common among young adults. Knowing that co-use amplifies intoxication and that the degree of amplification predicts future problematic use provides a basis for targeted harm reduction messaging.
The numbers in context
155 young adults tracked over 12 months. Co-use produced greater intoxication than either substance alone. Co-use within 0-30 minutes produced the greatest stimulation and bad effects vs cannabis alone. Co-use within 0-90 min had higher intoxication vs cannabis alone. Co-use within 0-120 min had higher intoxication vs alcohol alone.
How the study worked
Longitudinal study of 155 young adults (mean age 21, 55.5% women) who co-used cannabis and alcohol. Ecological momentary assessment (EMA) over 21 days at baseline captured real-time co-use and subjective effects. Follow-up assessments at 6 and 12 months measured hazardous cannabis use.
What this study cannot tell us
Self-reported subjective effects via EMA. Relatively small sample. Cannot control for doses of each substance. Young adult sample may not generalize to older adults.
How to read the evidence
Moderate: prospective design with ecological momentary assessment capturing real-time effects, though relatively small sample
When this study was published
Published in 2025
The bigger picture
Understanding that the timing between cannabis and alcohol use matters for intoxication levels provides practical harm reduction information. The link between co-use intoxication and future hazardous use suggests that co-use patterns could be an early warning sign.
Questions still open
- What drives the heightened intoxication during co-use? Would harm reduction messaging about timing of use change behavior? Are there individual differences in vulnerability to co-use amplification?
Common questions
Is mixing cannabis and alcohol more dangerous?
Does the timing between substances matter?
Read the original research
The association between cannabis and alcohol co-use and momentary subjective effects: Risks for increasingly hazardous cannabis use.
Drug and alcohol dependence, 269, 112595
Citation
Bedillion, Margaret F; Ansell, Emily B. (2025). The association between cannabis and alcohol co-use and momentary subjective effects: Risks for increasingly hazardous cannabis use.. Drug and alcohol dependence, 269, 112595. https://doi.org/10.1016/j.drugalcdep.2025.112595
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