Smoked cannabis reduces immediate alcohol consumption in controlled laboratory trial

Smoked cannabis directly reduced the amount of alcohol heavy drinkers consumed during a controlled laboratory experiment. The research indicates that acute marijuana intoxication may decrease the immediate urge to drink and delay the onset of alcohol consumption. These findings were published in the American Journal of Psychiatry.

Public health experts track the concurrent use of alcohol and cannabis closely. Across the country, expanding legalization has made cannabis the most popular psychoactive substance after tobacco for people who consume alcohol. Many individuals engage in both habits, and a strong overlap exists between those who struggle with alcohol use and those who face challenges regulating their cannabis intake.

In recent years, a social trend has emerged where people attempt to manage their alcohol habits by substituting cannabis instead. Pop culture sometimes refers to this practice as becoming “California sober.” This movement aligns with a broader push toward harm reduction, and it has fueled a rapid expansion in the market for cannabis-infused beverages marketed as alcohol alternatives.

Despite this cultural shift, previous observational studies produced conflicting results regarding how cannabis impacts alcohol consumption. Some research suggested that using cannabis leads to heavier drinking and worse treatment outcomes for those trying to quit alcohol. Other surveys indicated that people drink less on days when they use cannabis before they consume alcohol.

Observational data can only reveal associations rather than direct cause and effect. To find more concrete answers, researchers needed a controlled setting to observe how cannabis alters drinking behavior in real time. Jane Metrik, a researcher at the Brown University School of Public Health, led a team of scientists to investigate this dynamic.

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The research team recruited 157 adults between the ages of 21 and 44 from the local community. These participants reported engaging in heavy episodic drinking at least once a month. They also used cannabis at least twice a week.

Metrik and her colleagues utilized a double-blind crossover experimental design. This structure meant that participants came into the laboratory strictly after abstaining from both substances. Over the course of three completely separate experimental days, participants received different testing conditions, acting as their own baseline controls.

During the sessions, laboratory staff provided participants with cannabis cigarettes. Depending on the day, the cigarette contained either a placebo with virtually no active ingredients, a moderate dose of 3.1 percent delta-9-tetrahydrocannabinol, or a higher dose of 7.2 percent delta-9-tetrahydrocannabinol. Medical staff monitored blood pressure and heart rates while collecting blood samples to confirm intoxication levels.

After smoking, participants experienced a cue reactivity procedure. The researchers brought them into a neutral room and gave them a glass of water to smell and sip. Later, staff brought the participants into a simulated bar environment and presented them with their favorite alcoholic beverage to evaluate their cravings.

Following the cue exposure, participants engaged in a two-hour alcohol choice task in the simulated bar. Staff provided subjects with the opportunity to consume up to eight miniature alcoholic drinks. To mimic real world decision making, the researchers offered participants a financial incentive of three dollars for every drink they chose to leave on the table.

The physiological measurements confirmed that the cannabis doses worked exactly as intended. Both the moderate and higher doses elevated participants’ heart rates and increased their subjective feelings of intoxication, happiness, and arousal. The placebo condition produced no such alterations in mood or biology.

When measuring the desire to drink, the results painted a nuanced picture. The researchers used a standard multipoint questionnaire to grade alcohol cravings, and the overall scores did not show statistically significant differences across the three cannabis conditions. However, when asked a single targeted question about having an immediate urge for alcohol, participants reported a notable drop in desire right after smoking the higher concentration cannabis.

The most definitive changes appeared during the simulated bar task. Following the placebo cigarette, participants drank the largest amount of alcohol. When participants smoked the moderate dose of cannabis, they consumed 19 percent less alcohol compared to the placebo day.

The higher concentration dose produced an even larger reduction. Participants who smoked the 7.2 percent cannabis cigarette drank 27 percent less alcohol than they did under the placebo condition. The difference in alcohol consumption between the two active cannabis doses was not statistically significant.

The higher concentration of cannabis altered the timing of drinking behavior alongside the volume consumed. Compared to the placebo day, smoking the stronger cannabis delayed the decision to start drinking by an average of 48 percent. Participants waited over half an hour to initiate drinking, whereas they started drinking much faster when given the dummy cigarette.

The researchers suspect a satiation effect might explain these behavioral shifts. People who combine alcohol and cannabis often do so to reach a specific level of intoxication. Once a person achieves a desired mental state through smoking cannabis, their motivation to seek out further impairment through alcohol may naturally diminish.

Brain chemistry may also play a major role in these outcomes. The main active compound in cannabis acts upon the endogenous cannabinoid system, a natural chemical network in the human body that regulates reward processing and motivation. Chronic exposure to cannabis causes the brain to reduce the density of these chemical receptors in an attempt to maintain balance.

Nearly all the participants in this trial used cannabis on a daily basis. The mandatory abstinence period before the placebo session might have put them in a mild state of withdrawal. This sudden deprivation could have increased the reward value of alcohol, prompting them to consume more drinks on the placebo day than they did when their brain’s receptors were satisfied by the active cannabis joints.

The findings are attached to several limitations. The cannabis distributed in the study contained much lower concentrations of active compounds than the products currently dominating commercial dispensaries. The experiment also specifically tested sequential use, where participants smoked prior to drinking, rather than simultaneous consumption or pairing cannabis with an initial alcohol prime.

Medical professionals recommend caution regarding these results. The findings show a clear reduction in immediate drinking, but this does not mean replacing alcohol with cannabis is a safe or proven medical treatment. Clinicians advise against viewing cannabis as a primary harm reduction strategy for severe alcohol issues until longitudinal trials map out the long-term safety and efficacy of the substitution model.

The study, “Acute Effects of Cannabis on Alcohol Craving and Consumption: A Randomized Controlled Crossover Trial,” was authored by Jane Metrik, Elizabeth R. Aston, Rachel L. Gunn, Robert Swift, James MacKillop, and Christopher W. Kahler.