A new controlled laboratory study suggests that smoking cannabis may significantly reduce how much alcohol people consume—at least in the short term—adding rare experimental evidence to the debate over whether “California sober” habits hold up under scientific scrutiny.
Published Wednesday in the American Journal of Psychiatry, the findings show that participants who smoked higher-potency cannabis drank roughly 27 percent less alcohol over a two-hour period compared to when they received a placebo joint. Those who used a lower-potency strain still drank 19 percent less. Cannabis users also tended to delay their first drink.
But despite the striking results, the researchers caution that the findings don’t justify recommending marijuana as a substitute for alcohol.
“We’re not ready to tell people seeking treatment for alcohol, go ahead and substitute cannabis, and it will work out for you,” said Jane Metrik, a Brown University behavioral science professor who led the study. “It is an important signal… but we need far more evidence.”
To capture real-world conditions while maintaining tight controls, Metrik’s team designed a “bar lab” complete with cushy seating, a tap system, music and each participant’s drink of choice. After smoking in a separate room—high-potency cannabis, low-potency cannabis or a placebo joint—participants spent two hours alone in the bar with access to eight miniature drinks.
The study builds on recent work from Colorado researchers who found that people who smoked at home and then visited a mobile lab nearby drank about 25 percent less and reported reduced cravings.
“This gives us more confidence that there’s a real effect here,” said Jeff Wardell, a psychology professor at York University not involved in the Brown study.
Still, scientists say the full picture is complicated. A subset of participants in previous studies actually drank more after using cannabis. And most subjects in Metrik’s experiment had cannabis use disorder, raising questions about how results translate to people whose primary struggle is alcohol.
“There’s a real risk that substitution may simply promote more cannabis use,” said Rajita Sinha, a Yale psychiatry professor. Cannabis is legal in many states but carries its own health risks, including cognitive impairment, psychiatric illness, and dependence.
With more Americans using cannabis to cut back on drinking—often without medical guidance—researchers say clearer answers are urgently needed.
“We see this all the time, and we don’t know what to tell them,” Metrik said. “There’s no clear messaging yet.”
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