Medical and recreational cannabis use is now legal in many parts of the world, but scientists are still uncovering its full effects on the human brain.
A groundbreaking study has now confirmed what many have suspected: heavy cannabis use may significantly impair working memory—a crucial mental skill that helps us function in daily life.
Unlike short-term memory, which simply involves recalling information, working memory allows us to hold and manipulate information actively.
It plays a critical role in reasoning, decision-making, and impulse control—all functions that determine how we navigate the world around us.
A team of researchers from institutions in the US and Canada conducted the largest-ever study on cannabis and cognitive function, analyzing over 1,000 young adults.
Using brain imaging and cognitive testing, they found that heavy cannabis use and recent consumption were linked to lower brain activity in key areas responsible for working memory.
This discovery could have profound implications for both recreational users and those who rely on cannabis for medicinal purposes.
It also raises important questions about long-term cognitive health and whether the effects of cannabis on memory are reversible.
The Largest Study of Its Kind
For decades, scientists have debated the impact of cannabis on cognitive function. Previous research hinted at a connection between cannabis and impaired brain activity, but studies were often limited in size or scope.
Now, this new study, published in JAMA Network Open, changes the game.
Researchers analyzed brain imaging scans and self-reported cannabis use habits from 1,003 young adults, focusing on how different levels of cannabis consumption affected brain activity during cognitive tasks.
The size of this study makes it the most comprehensive examination of cannabis and brain function to date.
To ensure accuracy, the team applied rigorous statistical methods, including a false discovery rate (FDR) correction to minimize false positives.
This approach helped them pinpoint the specific cognitive functions most affected by cannabis use.
The findings were clear: working memory was the primary cognitive function negatively impacted by cannabis use.
Other brain functions—including reward processing, emotional regulation, language skills, and motor control—showed no significant differences between cannabis users and non-users.
Breaking the Common Assumptions About Cannabis
For years, many believed that cannabis primarily affected mood and relaxation, with minimal long-term effects on cognitive function. This study challenges that notion.
Brain scans showed reduced activity in critical regions associated with decision-making, attention, and emotion processing, including:
- The dorsolateral prefrontal cortex
- The dorsomedial prefrontal cortex
- The anterior insula
These regions have a high density of CB1 receptors, which are the primary targets of tetrahydrocannabinol (THC)—the psychoactive compound in cannabis.
In heavy users, these receptors become desensitized, leading to a noticeable decline in brain function during tasks requiring working memory.
Previous studies suggested that reduced brain activation in these areas might be temporary and linked to recent cannabis use.
However, the new research demonstrated that even individuals who had no cannabis in their system at the time of testing still showed signs of impaired brain activity.
This raises an important question: Are the effects of cannabis on working memory reversible, or do they cause lasting changes to the brain?
While this study doesn’t provide a definitive answer, it suggests that chronic cannabis use could have a longer-lasting impact than previously assumed.
Does Cannabis Withdrawal Also Affect Cognition?
The findings also introduce another challenge: if cannabis impairs working memory, does quitting suddenly improve it?
The answer isn’t so simple. According to lead researcher Joshua Gowin from the University of Colorado Anschutz Medical Campus, quitting cannabis cold turkey might not immediately restore cognitive function.
In fact, withdrawal symptoms could temporarily worsen cognitive performance, making it harder for users to regain full brain function in the short term.
For heavy users, sudden abstinence can lead to brain fog, anxiety, and difficulty concentrating—all of which might offset the potential benefits of quitting.
This means that reducing cannabis consumption gradually might be a better approach for those concerned about their cognitive health.
What This Means for Cannabis Users
The implications of this study are wide-ranging. As cannabis use becomes more common worldwide, users and healthcare professionals must consider its potential risks alongside its well-documented benefits.
For medical cannabis users, particularly those who rely on it for chronic pain, anxiety, or sleep disorders, this research suggests that long-term use could come with cognitive trade-offs.
It may be wise to monitor dosage and frequency of use to minimize any negative impact on working memory.
For recreational users, particularly young adults whose brains are still developing, this study reinforces the importance of responsible consumption.
Using cannabis occasionally may not lead to lasting cognitive impairment, but frequent or heavy use could have more significant effects on brain function over time.
More Research Is Needed
Despite these findings, many questions remain unanswered. Scientists still need to determine:
- How long-lasting the cognitive effects of cannabis are
- Whether brain function fully recovers after stopping cannabis use
- If certain individuals are more vulnerable to memory impairment than others
As cannabis legalization expands globally, studies like this will become increasingly important.
A better understanding of cannabis’s effects will help shape public health guidelines, inform medical recommendations, and ensure people make well-informed choices about their use.
“By studying cannabis’s effects on brain function, we can provide a well-rounded understanding of both its benefits and risks,” says Gowin.
“This empowers people to make informed decisions and fully comprehend the potential consequences of long-term cannabis use.”
For now, the takeaway is clear: cannabis affects working memory more than previously thought, and heavy users should be mindful of how it impacts their cognitive health.
References
- Gowin, J. et al. (2025). “Cannabis Use and Working Memory: Neural Correlates in Young Adults.” JAMA Network Open.
- National Institute on Drug Abuse (NIDA). “The Effects of Cannabis on the Developing Brain.” (2024).
- Harvard Medical School. “Marijuana and the Brain: What We Know So Far.” (2023).
