A feeling of relaxation. An altered sense of time and space. A slowed reaction time. These effects are all associated with cannabis, but what else do we understand about the drug’s effects on the brain?
Investigating the impacts of the drug, recent research in JAMA Network Open has revealed that heavy cannabis use is associated with reduced brain activity during working memory tasks. Representing the largest of any such study so far, the research indicates that the negative outcomes that are linked with heavy cannabis use are not as inconsequential as commonly thought.
“As cannabis use continues to grow globally, studying its effects on human health has become increasingly important,” said Joshua Gowin, a study author and an assistant professor at the University of Colorado Anschutz Medical Campus, according to a press release. “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.”
Read More: Weed Might Not Make You Creative After All
Ties Between Cannabis and Brain Activity
According to the study, cannabis use is rising, as more and more states and countries allow its production and sale. But as the drug’s prevalence increases, so, too, does the perception that cannabis is innocuous, whether used recreationally or medically.
To address this perception, and to examine the cognitive effects of cannabis, Gowin and a team of researchers turned to the brains of around 1,000 young adults. Monitoring their brain activity with magnetic resonance imaging (MRI), they revealed that around 63 percent of heavy cannabis users demonstrated reduced brain activity during working memory tasks. They also revealed that their reduced brain activity during those tasks was associated with poor performance.
Defined as the mind’s short-term storage system, the working memory allows people to manage and manipulate information temporarily. Though the research cannot reveal whether cannabis caused the reduced brain activity and poor working memory performance, the researchers say their results call out the negative outcomes that are associated with heavy cannabis use.
“People need to be aware of their relationship with cannabis,” Gowin said in the release. “Heavy users may need to be more cautious.”
Read More: What Science Knows About Marijuana's Health Benefits
Testing the Ties
According to the researchers, the associations between cannabis use and brain activity during working memory tasks were statistically significant in heavy cannabis users. While these users were defined as those who had used cannabis over 1,000 times throughout their lives, moderate users had used the drug 10 to 999 times and non-users had used the drug fewer than 10 times.
The researchers also studied the associations between cannabis use and brain activity during other tasks, including motor tasks, language tasks, and emotion and reward tasks, though the ties were not statistically significant.
Not only that; the researchers tested the associations between cannabis use and brain activity in recent cannabis users, too. These users were identified through drug testing, though the links between their cannabis use and brain activity during working memory and motor tasks did not survive a statistical analysis meant to minimize false positives.
"We applied the highest standards to our research, setting rigorous thresholds for statistical significance,” Gowin said in the release. “While some of the other tasks indicated potential cognitive impairment, only the working memory task showed a statistically significant impact.”
Demonstrating reduced brain activity during working memory tasks in the dorsolateral prefrontal cortex, the dorsomedial prefrontal cortex, and the anterior insula, heavy cannabis users saw activity diminish in the areas of the brain that are associated with memory, decision-making, and attention.
“There are a lot of questions we still need answers to regarding how cannabis impacts the brain,” Gowin said in the release. “Large, long-term studies are needed next to understand whether cannabis use directly changes brain function.”
Read More: Marijuana Could Help Reduce Depression and Anxiety
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
JAMA Network Open. Brain Function Outcomes of Recent and Lifetime Cannabis Use
Sam Walters is a journalist covering archaeology, paleontology, ecology, and evolution for Discover, along with an assortment of other topics. Before joining the Discover team as an assistant editor in 2022, Sam studied journalism at Northwestern University in Evanston, Illinois.
