⬇️ Prefer to listen instead? ⬇️
- Heavy cannabis use linked to reduced brain activity during memory tasks.
- Changes in cognitive function persisted even without recent use.
- Specific brain areas with many cannabinoid receptors showed the most impact.
- Brain inefficiencies were more related to usage frequency than addiction diagnosis.
- Potential differences between men and women in cannabis-related brain effects.
As cannabis use becomes more common, researchers are paying more attention to what it does to the brain over time. One big worry is that heavy cannabis use might change brain activity and memory, even after the high feeling is gone. New research suggests that using a lot of cannabis often could cause lasting changes in how the brain handles information. This raises concerns about thinking skills, clear thinking, and everyday memory.
The Study at a Glance
A recent study in JAMA Network Open gives us important information about how heavy cannabis use may change brain activity, especially related to memory.
The study used information from the Human Connectome Project, with over 1,000 adults aged 22 to 37. These people were grouped by how much cannabis they had used, from people who never used it to heavy users who had used it more than 1,000 times in their lives. Researchers used functional magnetic resonance imaging (fMRI) to watch how people's brains reacted to tasks for memory, reasoning, motor skills, handling emotions, and social thinking.
The main question was: Do heavy cannabis users' brains work differently, even when they aren't high?
Key Finding: Lower Brain Activity in Heavy Cannabis Users
The study clearly said yes. When doing working memory tasks, heavy cannabis users showed much less activity in key brain areas known for managing complex thinking
- Dorsolateral Prefrontal Cortex (DLPFC): This area helps with attention, reasoning, and working memory.
- Medial Prefrontal Cortex (mPFC): This area is involved in making choices, handling emotions, and social thinking.
- Anterior Insula: This complex area is involved in awareness, feelings, and sensing your body's internal state.
These areas have a lot of cannabinoid receptors (CB1 receptors), which react to THC—the main psychoactive part of marijuana. Over time, being exposed to THC regularly may make these receptors less sensitive or change them, reducing how the brain cells react during tasks that require thinking.
This lower activity doesn't mean the brain stops working, but it does suggest that the brain has to work harder—or might not work as well—when the mind is busy.
Short-Term vs. Long-Term Effects: A Separation
One of the most important things this study shows is that these effects weren't just short-term from being high on cannabis. Even people who had not used cannabis for at least 10 days (proven by urine tests) still showed less brain activity if they were heavy users long-term.
This suggests a lasting effect on brain function that stays even after the "high" is gone. So, heavy cannabis use may leave a mark on the brain that keeps affecting thinking skills for a long time after users feel "sober."
Brain scientists call this kind of pattern a trait effect rather than a state effect. A trait effect is about long-term changes likely caused by regular use, not just temporary changes from being intoxicated.
Working Memory and Everyday Cognitive Demands
Working memory is one of the most basic and important thinking skills. It lets us
- Hold and use information in our minds for a short time (seconds to minutes)
- Learn new things or take in information
- Plan and do things, and check how we are doing
- Make decisions
- Focus when there are distractions
The study found that people who used cannabis heavily had less brain activity in areas responsible for working memory. Not surprisingly, this meant they did worse on memory and verbal learning tasks. They might seem fine on the outside, but their brains could be under more stress or not working as well in normal situations—like following directions, remembering conversations, or staying organized.
Signs of Subtle Cognitive Impairment Without Intoxication
It's important to note that reduced brain performance was seen even in users who were not currently high. People who had recently stopped using cannabis still had thinking problems, especially with
- Working memory tests (like holding and using information)
- Verbal memory tasks (like remembering words or language patterns)
This is important in a medical sense. It means that thinking problems can go unnoticed, affecting things from school and work to managing emotions and planning for the future—without clear signs of being high.
As cannabis becomes more legal and used for medical reasons, these findings remind us to think about cannabis not just for its immediate effects, but also for how it might still affect our minds in ways that shape daily life.
Usage Frequency Matters More Than Addiction Diagnosis
Another key finding was that differences in brain activity were not strongly tied to being diagnosed with cannabis use disorder or dependence. Instead, how often someone used cannabis over their lifetime was more important.
In other words, someone might not be addicted in a medical sense but could still have changes in brain activity if they've used cannabis a lot, especially for many years. The study highlights that how much and how often someone uses cannabis could be more important for brain health than whether they are seen as "dependent" or not.
This is different from common ideas, which tend to see substance use effects mainly through the idea of addiction. Here, cannabis use seems to slowly reduce thinking efficiency based on amount and time, not just addiction patterns.
Social Cognition May Be Vulnerable Too
While memory got much of the attention, researchers also looked at how cannabis affects social cognition—our ability to understand social situations and interactions, like understanding other people's feelings and intentions.
The results first showed a link between recent cannabis use and worse performance on social cognition tasks, but this link got weaker when they considered things like race and education. Still, it's an interesting hint that needs more study.
Social reasoning is key to making relationships, dealing with disagreements, and showing empathy. If cannabis gets in the way of the brain's ability to handle this kind of complex information, it could have big effects on emotional intelligence and how well people get along with others—especially for young adults.
Sex-Based Differences in Motor Function Effects
One of the more surprising things the study found was a difference between men and women in how cannabis affected brain tasks related to movement.
- In recent users, men showed much less brain activity in motor areas during movement tasks.
- Women, on the other hand, did not show the same drop—suggesting that there might be something protecting women or a biological difference in how women's brains react to THC when it comes to motor skills.
We don't yet know why this sex-based difference happens, but it could involve hormones, differences in cannabinoid receptors, or different ways men and women regulate dopamine.
This finding shows we need to study cannabis differently for men and women, not just by how often they use it, but also by biological sex. Until we know more, men might need to be extra careful about how recent cannabis use affects their motor control, especially for things that need coordination (like driving, sports, or physical work).
Brain Efficiency and Cognitive Performance
Beyond just seeing changes in brain activity, researchers looked at whether this lower activity was related to how well people actually did on thinking tasks—and it was.
In people with less brain activity during memory tasks, scores were also lower on standard tests of
- Verbal memory
- Working memory
- General intelligence
This supports the idea that brain efficiency—how much energy or brain activity it takes to do a task—is linked to how well people do on intelligence tests.
Less activity in certain brain areas might mean that the brain is not working as well or is using fewer, less good brain networks to do tasks. This idea is often used in aging research, where using extra effort or not being efficient is often a sign of thinking decline.
The Study’s Limitations: A Realistic Perspective
While this study is interesting, it had some limits
- It was cross-sectional, meaning it looked at people at one point in time, not over a longer period.
- It didn't fully separate out how other substances (alcohol, nicotine, etc.) or mental health issues (like ADHD or depression) might have affected the results.
- We can't say for sure that cannabis caused the brain changes, only that they are related.
Even so, the consistent link between heavy cannabis use and lower brain activity—even when THC is gone from the body—is worth paying attention to and being careful for users who care about their brain health.
Optimize Sleep and Hydration
Not sleeping well hurts working memory, attention, and handling emotions. Also, not drinking enough water reduces thinking skills. Try to get 7–9 hours of sleep and at least 2 liters of water every day.
Practice Mindfulness and Meditation
Practices like focused breathing and guided meditation can improve attention, emotional control, and even the size of the hippocampus—a brain area connected to memory.
Mushrooms that may help brain function
Supplements like lion’s mane mushroom have become interesting because they may help nerve growth factor (NGF), which helps brain cells repair and adapt. Studies are looking at if it can help prevent or slow down thinking decline.
Other supplements like L-theanine, omega-3 fatty acids (especially DHA), and citicoline may also help brain function.
Feed Your Brain Right
Foods with antioxidants, omega-3s, and polyphenols can help reduce brain inflammation and help the brain adapt. Blueberries, dark chocolate, turmeric, and walnuts are good for the brain.
Responsible Cannabis Use: A Balanced Perspective
Research suggests that using cannabis in moderation and with breaks might lessen some of the thinking problems. Here are some practical tips for using cannabis mindfully
- Keep track of how much you use in total—not just how often each week, but over your lifetime.
- Choose strains with lower THC if you can, or mixes with CBD to make it less strong.
- Take “tolerance breaks” to let your brain's cannabinoid receptors get back to normal.
- Use other wellness methods along with cannabis, like adaptogenic herbs, better sleep habits, and creative hobbies.
Why This Matters for Young Adults and Lifelong Brain Health
This research is especially important for young adults, whose brains are still developing until their mid-to-late 20s. Using a lot of cannabis before the brain is fully developed could affect their long-term path in school, work, and mental health.
But it's also important for everyone: in a culture that values being efficient, productive, and clear-headed, understanding how heavy cannabis use changes brain activity is a key part of taking care of our minds.
Memory, Mushrooms, and Mindfulness
In a world where cannabis, mushrooms, and mental health are all popular topics, it's key to remember one main point: your brain can adapt, but it's not unbreakable. Heavy cannabis use seems to change brain activity in ways that could harm memory and overall thinking skills.
So whether you use cannabis often, are interested in brain enhancement, or want to be healthy in a natural way, think about adding supportive habits like functional mushrooms, mindfulness, and good nutrition to your life.
If your brain is your most valuable tool—and it is—learning how to protect and strengthen it is worth doing.
Citations
- Gowin, J. L., Ellingson, J. M., Karoly, H. C., Manza, P., Ross, J. M., Sloan, M. E., Tanabe, J. L., & Volkow, N. D. (2024). Brain Function Outcomes of Recent and Lifetime Cannabis Use. JAMA Network Open, 7(4). https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2829657
