Researchers Report that Cannabis Use May Impair Working Memory

Researchers from the University of Colorado report that cannabis use impacts brain function during cognitive tasks, significantly affecting working memory among young adults. The research, conducted on over 1,000 participants aged 22 to 36, is the largest study of its kind and utilized brain imaging technology to assess the relationship between cannabis use and cognitive performance.  

“As cannabis use continues to grow globally, studying its effects on human health has become increasingly important,” says Joshua Gowin, lead author of the study.  

The findings, published on JAMA Network Open. indicate that 63% of heavy lifetime cannabis users and 68% of recent users exhibited reduced brain activity during a working memory task. Working memory, which enables individuals to retain and manipulate information to complete tasks such as solving problems or following instructions, was found to decline alongside brain activity in certain regions, including the dorsolateral prefrontal cortex, dorsomedial prefrontal cortex, and anterior insula. These areas are critical for decision-making, attention, and emotional regulation.  

The study categorized heavy cannabis users as individuals who reported using the substance more than 1,000 times in their lifetime. Moderate users were those with 10 to 999 instances of use, while nonusers reported fewer than 10 uses. Participants underwent magnetic resonance imaging (MRI) while completing seven cognitive tasks designed to test various brain functions, including emotion, motor skills, language, and relational assessment. Among these, only working memory showed a statistically significant decline linked to cannabis use.  

While some cognitive tasks suggested potential impairments, the impact on working memory was the only result deemed statistically significant. Researchers also explored the possibility of mitigating these effects through abstinence. Gowin says that avoiding cannabis use before cognitive tasks might improve performance, although he cautioned against abrupt cessation, which could also disrupt cognition in heavy users.