Can Cannabis Help People Drink Less Alcohol? What a New Study Found

A federally funded study tested the “substitution” idea in a real-world setting.

Could using cannabis help some people cut back on drinking? It's an idea that's gained attention as cannabis becomes more widely legal — sometimes called the “substitution” effect. A 2025 study, funded by the National Institutes of Health, set out to test it directly, and the results are genuinely interesting — with some important nuance.

How the Study Worked

Researchers from Colorado State University and the University of Colorado recruited about 60 adults who were heavy drinkers and who also used cannabis regularly — an important point: this was not a general-population sample. Each participant completed two sessions. In one, they were offered alcohol alone — a “priming” drink followed by the option of up to four more, offered at 15-minute intervals. In the other, they first used their own legal-market cannabis, at a dose of their choosing, before being offered alcohol the same way.

One detail makes the study unusually real-world: because federal restrictions bar handling legal cannabis in university labs, the sessions were run in a mobile laboratory parked outside participants' homes. People used their own products at their usual doses, which is closer to real life than a standardized lab dose.

What They Found

Across the whole group, using cannabis before drinking was associated with significantly less alcohol consumed. On average, participants had about two self-administered drinks in the alcohol-only session, dropping to roughly 1.5 when cannabis came first — about a 25% reduction. Co-using cannabis and alcohol was also associated with a significant short-term drop in alcohol craving compared to alcohol alone.

The Crucial Caveat: It Didn't Work for Everyone

Here's the part that the headline version of this story often leaves out, and it matters. When researchers looked closer, the effect was concentrated in one subgroup. About 23 participants — whom the researchers called “substituters” — drank significantly less after cannabis and showed a consistent drop in craving. But for the participants who drank the same amount or more after cannabis, craving levels stayed flat or actually increased. In other words, cannabis didn't reduce drinking for everyone — and for some, it may not have helped at all.

Interestingly, the difference didn't appear to be about THC dose. Blood tests showed no significant THC difference between those who cut back and those who didn't, which suggests the effect, where it occurred, may have less to do with chemical potency and more to do with individual factors and context.

How to Read This

This is a well-designed study and a real contribution — the researchers describe it as the first to test the effects of legal-market cannabis on alcohol intake. It adds to other research pointing the same direction, such as work by Karoly and colleagues finding reduced drinking on cannabis-use days.

But it's important not to over-read it. It was a single laboratory study in a specific group — heavy drinkers who already use cannabis regularly — and the researchers themselves frame cannabis as a potential substitute “for some individuals,” not a proven treatment. Using cannabis to manage problem drinking is not a self-directed strategy anyone should adopt on their own: both substances carry their own risks, and combining them has risks of its own. If drinking is a concern for you or someone you know, the most reliable path is a conversation with a healthcare provider or an addiction specialist, who can look at the full picture. In the U.S., the SAMHSA National Helpline (1-800-662-4357) offers free, confidential support.

Reference: Cannabis administration is associated with reduced alcohol consumption: Evidence from a novel laboratory co-administration paradigm. Drug and Alcohol Dependence, 2025. Colorado State University and University of Colorado; funded by the NIH National Institute on Alcohol Abuse and Alcoholism.

This article is for general information only and is not medical advice. Cannabis is not an approved treatment for alcohol use disorder. If you are concerned about your drinking, please consult a qualified healthcare professional.