A new study released today in JAMA Network Open examines how both recent and long-term cannabis use affects brain function while performing cognitive tasks.
This research, the largest of its kind to date, assessed the impact of cannabis on over 1,000 young adults aged 22 to 36 through brain imaging technology. The findings revealed that 63% of those categorized as heavy lifetime cannabis users showed decreased brain activity during a working memory exercise, while 68% of users who had used cannabis recently exhibited a similar effect.
A decline in brain activity correlated with poorer working memory performance, which is the capacity to hold and utilize information for task completion. For instance, working memory is crucial for following recently given instructions or mentally visualizing and adjusting information, such as when solving a math problem.
“As cannabis consumption increases worldwide, it is vital to investigate its effects on human health. This understanding aids in recognizing both the advantages and disadvantages of cannabis, enabling individuals to make well-informed choices and grasp the potential consequences,” stated Joshua Gowin, PhD, the lead author of the study and an assistant professor of radiology at the University of Colorado School of Medicine located on the Anschutz Medical Campus.
In the context of this study, heavy users are defined as those who have consumed cannabis over 1,000 times throughout their lives, while moderate users are those with 10 to 999 experiences, and individuals who have used it fewer than 10 times are classified as nonusers.
The research team analyzed the neural responses of participants during MRI sessions and assigned them seven cognitive challenges, which evaluated working memory, reward processing, emotions, language skills, motor abilities (like finger tapping to assess brain control), relational reasoning, and theory of mind.
They found that cannabis use significantly affected brain function during working memory tasks, indicating that the impact observed is unlikely to be a fluke. This effect was noted for both recent and long-term cannabis users, although the influence was less pronounced in the other cognitive tasks.
“We adhered to the highest research standards, applying strict criteria for statistical relevance across all seven cognitive tests. To reduce the chances of false positives, we implemented false discovery rate (FDR) corrections. While other tasks suggested possible cognitive impairment, only the working memory task demonstrated a statistically significant effect,” Gowin added.
During working memory challenges, the researchers observed that heavy cannabis use seemed to diminish brain activity in specific areas, including the dorsolateral prefrontal cortex, dorsomedial prefrontal cortex, and anterior insula. These brain regions play crucial roles in cognition, such as decision-making, memory, attention, and emotional processing.
However, Gowin pointed out that their findings also indicate that refraining from cannabis use before engaging in cognitive tasks might enhance performance. “Individuals should consider their relationship with cannabis, as going cold turkey might also interfere with their cognition. Heavy users may need to exercise caution,” he noted.
He concluded, “Numerous questions remain to be explored regarding the effects of cannabis on the brain. Future large-scale, long-term studies are essential to determine whether cannabis use directly alters brain function, how long these effects persist, and their impact across different age demographics.”
