GO FOR IT –
Dec. 4, 2025 – The study, published in the American Journal of Psychiatry in November, is one of the first to isolate how an individual’s alcohol consumption is acutely affected by their consumption of cannabis. Using a randomized, double-blind, crossover design, each participant smoked cannabis cigarettes with varying levels of THC — the main psychoactive compound in marijuana — across different sessions.
The study also distributed placebo cigarettes in some sessions. In other research designs, “you don’t have a placebo control,” Metrik said, adding that performing a randomized clinical trial was necessary to say for sure that cannabis usage directly causes a reduction in alcohol consumption.
“Everybody in the study got all the conditions so that you can test how cannabis affects alcohol within the same person,” she explained. “You eliminate any kind of variability between people that way.”
“This is gold standard evidence that (lets us) talk in causal terms,” Metrik added.
After smoking their assigned cannabis cigarettes, participants completed an alcohol choice task, during which they could drink as much or as little as they wanted, up to a blood alcohol concentration of 0.10. The study found that participants who smoked larger amounts of THC cannabis drank less alcohol.
But the findings generally challenge previous understandings of substance use. When Metrik first proposed the study nearly a decade ago, she hypothesized that cannabis use would actually increase alcohol consumption.
