Using cannabis to cut back on alcohol? Your working memory might dictate if it works

A study of individuals reporting heavy alcohol and cannabis use found that individuals with average and higher working memory tend to have a significantly lower urge to drink alcohol after smoking cannabis with 7.2% THC compared to a placebo. This effect was absent when the THC concentration in the cannabis was 3.1%. Lower working memory capacity was associated with a higher urge to drink alcohol overall. The research was published in Addictive Behaviors.

Alcohol use disorder is a medical condition characterized by a problematic pattern of alcohol use that leads to significant impairment or distress. It involves symptoms such as difficulty controlling drinking, strong cravings for alcohol, continued use despite negative consequences, and tolerance or withdrawal.

Studies indicate that 47.5% of individuals over the age of 12 in the U.S. report alcohol use in the past month, and 10.2% of those reporting past-year alcohol use meet the criteria for alcohol use disorder. Many individuals who use alcohol heavily also tend to use cannabis.

Studies have found that the coadministration of alcohol and delta-9 tetrahydrocannabinol (THC), the primary psychoactive cannabinoid in cannabis, enhances the pleasurable effects of both substances. This learned or pharmacological response can cause cannabis use to trigger the urge to drink.

Study author Rachel L. Gunn and her colleagues wanted to explore how cannabis consumption is associated with alcohol urge and whether working memory capacity moderates this association. They analyzed data from the clinical trial NCT02983773 (Principal Investigator: J. Metrik).

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Study participants were 125 individuals between 21 and 44 years of age reporting heavy alcohol use and using cannabis at least twice per week. Thirty-two percent of them were women.

These individuals first completed a baseline session following overnight cannabis abstinence. During this session, they reported their demographic data and recent substance use history, and completed an assessment of their working memory capacity (using N-back tasks, and complex span tasks—specifically, operation span and symmetry span). Working memory capacity is the amount of information a person can actively hold and manipulate in their mind at one time while performing cognitive tasks such as reasoning, learning, or problem-solving.

Next, they completed three experimental sessions. In these sessions, they smoked a placebo (a cannabis cigarette with no THC), cannabis with 3.1% THC, and cannabis with 7.2% THC. The order of these sessions was counterbalanced so that each of these treatments was equally likely to be the first, second, or third session (to control for any order effects).

Before and after smoking, participants reported their alcohol urge. The cannabis cigarettes were rolled at both ends and administered via a paced puffing procedure (i.e., participants were instructed to inhale the cannabis smoke in a controlled pattern).

Results showed that participants with average and higher working memory capacity, as measured by the symmetry span task, tended to have a significantly lower alcohol urge after smoking 7.2% THC compared to the placebo, but not after smoking 3.1% THC cannabis. Performance on the operation span task was not associated with alcohol urge. Lower working memory capacity, as determined by the N-back tasks, was associated with a higher alcohol urge overall, but N-back scores did not moderate the impact of cannabis on alcohol urge.

The N-back task is a memory test where people see or hear a series of items and must say when the current one matches something shown a few steps earlier. The operation span task asks people to solve simple math problems while trying to remember a list of letters, testing how well they can multitask mentally. The symmetry span task involves judging whether visual patterns are symmetrical while remembering the locations of shapes on a grid, measuring visual working memory.

“Findings suggest individuals with higher but not lower working memory experience lower alcohol urge under acute effects of cannabis. Although cannabis is increasingly perceived as a substitute for alcohol, individuals with lower working memory may be less likely to experience such benefits when attempting to reduce their drinking**,” the** study authors concluded.

The study sheds light on the psychological effects of cannabis in heavy co-users of alcohol and cannabis. However, it should be noted that working memory capacity was measured using three different types of tasks, and the results depended on the type of task used. Working memory capacity can also fluctuate over time depending on a person’s state. Finally, the study authors explored the effects of cannabis on alcohol urge immediately after smoking cannabis. It remains unknown how long the detected effects last.

The paper, “Working memory capacity predicts cannabis-induced effects on alcohol urge,” was authored by Rachel L. Gunn, Lindy K. Howe, Holly K. Boyle, and Jane Metrik.