College Students Drank More Heavily on Days They Also Used Cannabis | Research

The takeaway

Young adults were more likely to engage in heavy and high-intensity drinking on days they co-used cannabis, with more cannabis use on a given day predicting heavier alcohol consumption.

College health professionals, addiction researchers, young adults

Heavy and high-intensity drinking were more likely on days when cannabis was also used

What the researchers found

Co-use days were associated with increased odds of both heavy episodic drinking (4+/5+ drinks) and high-intensity drinking (8+/10+ drinks) compared to alcohol-only days. On co-use days, heavier drinking was more likely when more cannabis was used. Greater use of flower (grams) and concentrate (hits) specifically predicted high-intensity drinking.

Why it matters

The combination of alcohol and cannabis is increasingly common among young adults, and this study shows the combination is associated with the most dangerous level of drinking. Understanding that co-use days are heavier drinking days could inform targeted intervention.

The numbers in context

318 participants; 54 daily surveys; increased odds of HID (8+/10+ drinks) and HED (4+/5+ drinks) on co-use vs alcohol-only days; more cannabis events per day predicted heavier drinking; more grams of flower predicted HID; more hits of concentrates predicted HID; HID vs HED did not differ between co-use and alcohol-only days

How the study worked

Daily diary study with 318 young adults from three US universities who reported simultaneous alcohol and cannabis use. Participants completed five repeated daily surveys over 54 consecutive days reporting drinks consumed, cannabis use frequency, forms, and quantity.

What this study cannot tell us

Self-selected sample from three universities may not represent all young adults, daily diary relies on self-report, cannot determine whether cannabis causes heavier drinking or both reflect a common tendency, only examined simultaneous use

How to read the evidence

Well-designed daily diary study with 54 measurement days, but self-selected university sample and self-report limitations

When this study was published

Published 2025

The bigger picture

High-intensity drinking (double the binge threshold) confers the greatest risk of acute consequences including blackouts, injuries, and alcohol poisoning. The finding that cannabis co-use is associated with these extreme drinking levels suggests prevention efforts should address the combination specifically.

Questions still open

Does cannabis use lead to heavier drinking, or do people who plan heavy drinking nights also use cannabis? Would reducing cannabis access on college campuses reduce high-intensity drinking? Do the health risks of combined use exceed what each substance alone would predict?

Common questions

Do people drink more when they also use cannabis?

In this study, college students were more likely to engage in heavy and high-intensity drinking on days they also used cannabis. More cannabis use on a given day predicted heavier alcohol consumption.

Does the type of cannabis matter for drinking levels?

Yes. Using more grams of flower and more hits of concentrates were both specifically associated with high-intensity drinking (8+/10+ drinks), the most dangerous level of alcohol consumption.

Read the original research

Examining the relationship between cannabis use and drinking levels on co-use days.

Alcohol, clinical & experimental research, 49(8), 1778-1791

View on PubMed ↗Publisher’s paper ↗

Citation

Boyle, Holly K; Sokolovsky, Alexander W; Gunn, Rachel L; Gette, Jordan A; White, Helene R; Jackson, Kristina M. (2025). Examining the relationship between cannabis use and drinking levels on co-use days.. Alcohol, clinical & experimental research, 49(8), 1778-1791. https://doi.org/10.1111/acer.70107