Simultaneous Alcohol and Cannabis Use Linked to More Alcohol Problems Than Using Them Separately | Research

The takeaway

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.

Harm reduction professionals, substance use researchers, and young adults who co-use alcohol and cannabis.

Same-day use without overlapping effects had 55-64% lower odds of alcohol-related consequences than simultaneous use

What the researchers 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.

Why it 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 numbers in context

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 the study worked

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.

What this study cannot 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.

How to read the evidence

Preregistered ecological momentary assessment provides strong within-person data, though the young adult sample and self-report measures limit generalizability.

When this study was published

2025 publication with 28-day daily diary data.

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.

Questions still open

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?

Read the original research

Simultaneous alcohol and cannabis use is associated with daily consequences reflective of alcohol use disorder symptoms.

Drug and alcohol dependence, 276, 112924

View on PubMed ↗Publisher’s paper ↗

Citation

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