A landmark study published Tuesday in JAMA Network Open found that both recent and lifetime cannabis use may impair brain function during cognitive tasks, particularly those involving working memory.

The study, the largest of its kind, examined 1,000 young adults aged 22 to 36 using brain imaging technology. Researchers found that 63% of heavy lifetime cannabis users showed reduced brain activity during a working memory task, while 68% of recent users exhibited a similar decline.

Implications For Memory And Cognitive Performance

Working memory plays a crucial role in everyday functions, allowing individuals to follow instructions, solve problems and process information efficiently. The decline in brain activity observed in cannabis users correlated with poorer performance on working memory tasks.

“As cannabis use continues to grow globally, studying its effects on human health has become increasingly important," said lead author Joshua Gowin, Ph.D., an assistant professor of radiology at the University of Colorado School of Medicine. "By doing so, we can provide a well-rounded understanding of both the benefits and risks of cannabis use, empowering people to make informed decisions and fully comprehend the potential consequences.”

A Thursday report by Julia Milzer for the Colorado Anschutz Medical Campus noted that the study categorized participants into three groups: heavy users who had consumed cannabis more than 1,000 times in their lifetime, moderate users who had consumed between 10 and 999 times and those who had used marijuana fewer than 10 times, essentially non-users.

Marijuana's Impact On The Brain

To assess brain function, researchers conducted MRI scans while participants completed seven cognitive tasks. The tests measured working memory, language skills, motor function, emotional processing, decision-making and social cognition. The latter refers to the processes that influence how people respond to social signals.

The most significant impact was observed in the working memory task, where cannabis users exhibited reduced brain activity in key regions, including the dorsolateral prefrontal cortex, dorsomedial prefrontal cortex and anterior insula. These areas are critical for memory, decision-making, attention and emotional regulation.

“We applied the highest standards to our research, setting rigorous thresholds for statistical significance across all seven cognitive function tests," Gowin said. "While some of the other tasks indicated potential cognitive impairment, only the working memory task showed a statistically significant impact."

Potential For Cognitive Recovery

While the study suggests that abstaining from cannabis before performing cognitive tasks may help improve function, Gowin cautioned against stopping abruptly.

“People need to be aware of their relationship with cannabis since stopping cold turkey could disrupt their cognition," he said. "For example, heavy users may need to be more cautious."

Looking ahead, researchers say even larger, long-term studies are needed to determine whether cannabis directly alters brain function, how long these effects last and how different age groups are affected.

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