Heavy cannabis use is linked to significant lower brain activity in certain regions, a new study found.

The research, which analyzed brain scans of more than 1,000 young adults, suggests that frequent users had lower activity in key memory and decision-making regions.

High Rate of Memory Problems Found in Users

New research involving more than 1,000 young adults finds that extensive use of cannabis over a lifetime is linked to decreased brain activation, especially during tasks that require working memory—the cognitive ability that allows us to work with information without losing track of what we’re doing.

Working memory is used when you remember a phone number while dialing it, mentally calculating a bill while shopping, keeping track of multiple steps in a recipe while cooking, holding a new person’s name in mind during a conversation, and so on.

The study, recently published in JAMA Network Open, used data from the Human Connectome Project, which included magnetic resonance imaging (MRI) results and self-reported cannabis use data from study participants, who were aged between 22 and 36 years.

In the study, heavy users are considered young adults who’ve used cannabis more than 1,000 times over their lifetime. Using cannabis 10 to 999 times was considered a moderate user, and less than 10 times was considered a nonuser.

As much as 63 percent of heavy lifetime cannabis users and 68 percent of recent users exhibited reduced brain activity during a working memory task. Changes in brain activity in recent users were insignificant.

In heavy lifetime cannabis users, brain regions affected included the anterior insula, medial prefrontal cortex, and dorsolateral prefrontal cortex. These areas of the brain have a lot of CB1 receptors, which bind THC, the active ingredient in cannabis. Studies in mice have shown that long-term exposure to THC can reduce CB1 receptors, which may explain why long-term cannabis users had less brain activity in these brain regions.

The Potential for Long-Term Effects on the Brain

The reduced brain activation suggests potential long-term effects of cannabis use on memory processing, according to the study’s first author Joshua Gowin, assistant professor of radiology at the University of Colorado School of Medicine.

The effects of reduced working memory activation may be long lasting, he stated.

These brain regions play an important role in how we combine our feelings with our thoughts, especially when making decisions, interacting socially, and managing our emotions.

“There are a lot of questions we still need answers to regarding how cannabis impacts the brain,” Gowin added. “Large, long-term studies are needed next to understand whether cannabis use directly changes brain function, how long these effects last and the impact on different age groups.”

Previous research has already linked cannabis use to a severe psychiatric condition. A 2019 study published in The Lancet Psychiatry found that daily use of cannabis, especially high-potency forms of the drug, is strongly linked with the onset of psychosis.

Regarding the relationship between cannabis use and other mental health disorders, Dr. Matthew Sherman, chief of adult outpatient psychiatry and behavioral health at Stony Brook Medicine, told The Epoch Times that based on his experience, co-occurring cannabis use with mental health disorders is prevalent and often adversely affects treatment outcomes.

The study also suggests that abstaining from cannabis before performing a cognitive task can improve performance. However, Gowin noted that abstinence may have its own set of consequences.

“People need to be aware of their relationship with cannabis since abstaining cold turkey could disrupt their cognition as well. For example, heavy users may need to be more cautious,” Gowin stated.