Summary: New research has uncovered a surprising link between cannabis use and brain health in middle-aged and older adults. In a large-scale study involving over 26,000 participants from the UK Biobank, researchers found that lifetime cannabis use in adults ages 40 to 77 was generally associated with larger volumes in specific brain regions and superior cognitive function.
Unlike the cognitive decline often associated with heavy use in adolescents, this older demographic—who often use cannabis for sleep or chronic pain—showed preserved brain volume in areas critical for memory and learning, such as the hippocampus. While the findings suggest a potential neuroprotective effect in aging, the researchers emphasize that the relationship is complex, with “moderate” use appearing to offer the most consistent benefits.
Key Facts
- Preserved Brain Volume: Cannabis users showed larger regional brain volumes in areas with high density of CB1 receptors, including the hippocampus, which is vital for memory and often shrinks with age and dementia.
- Cognitive Boost: Participants with a history of cannabis use performed better on tests measuring learning, memory, processing speed, attention, and executive function.
- The “Moderate” Advantage: The most significant positive effects were seen in the moderate-use group, suggesting a dose-dependent relationship where more is not necessarily better.
- Complex Regional Effects: While most regions showed positive results, the posterior cingulate (part of the limbic system) actually showed lower volume in users, highlighting the nuanced impact of the drug.
- Demographic Shift: The study highlights a growing trend of older adults using cannabis for therapeutic reasons, a group that has historically been understudied compared to younger users.
Source: University of Colorado
Research studying the effects of cannabis on the brain has often focused on adolescents, but a new study from CU Anschutz researchers looks at population-level impacts of cannabis usage on the brain in older adults.
“More older adults are using cannabis. It’s more widely available and is being used for different reasons than in younger folks – such as for sleep and chronic pain,” said Anika Guha, PhD, a clinical psychologist and faculty research associate in the Department of Psychiatry at CU Anschutz.
“Plus, people are living longer. We have to be asking, ‘What are the long-term effects of cannabis use as we continue to age?’”
The research team found that cannabis usage in older adults was generally associated with larger volumes in several brain regions and better cognitive function in adults ages 40 to 77.
Guha said she was surprised by the extent of the positive findings. But she emphasized that cannabis use studies are difficult with often unknown variables, noting the constituents and potency of the cannabis products study subjects used were unknown.
“We’re really interested in thinking about both the benefits and risks and understanding this drug in the context of mental health, dementia and more,” said Guha. “There’s so much more to explore.”
In the following Q&A, Guha details the study’s findings, the complexities of studying relationships between brain function and cannabis, and why nuanced discussion around studying the drug is critical.
What did you and the team find on the impact cannabis has on brain function for older adults?
The big-picture, overall finding was that greater lifetime cannabis use among middle aged and older adults (a total of 26,362 participants ages 40 to 77, with an average age of 55) was generally associated with larger brain volumes and better cognitive function.
Specifically, we assessed brain regions that are associated with higher cannabinoid receptor – CB1 – density, which we thought would likely be impacted by cannabis use. We also looked at domains of cognitive function that have been associated with cannabis use in the past, including learning and memory, processing speed, attention and executive function.
One of the phrases used in the paper was that cannabis was associated with increased regional brain volume. Can you walk us through what that is?
It refers to the fact that we were investigating specific parts of the brain and looking at their individual volumes, as opposed to overall or total brain volume.
Some studies will just say there was an impact of cannabis on overall gray matter. However, we wanted to take a more nuanced approach by looking at effects on specific brain regions, especially those with high CB1 receptor density, as well as on cognitive processes like memory, which is, of course, very relevant to aging.
For example, the hippocampus was one of the regions we looked at since it contains many CB1 receptors and plays an important role in memory, especially as we age, and is also implicated in dementia.
What does it mean to have bigger brain volumes? It’s not that bigger is always better, but we also know that as we age, we often see smaller brain volumes due to processes like atrophy and neurodegeneration. That decrease is often correlated with reduced cognitive function and increased dementia risk.
In this study, we did see that most of the brain regions we looked at demonstrated a positive relationship between brain volume and cognitive performance. So in this sense, we could think of larger brain volumes in the context of aging as possibly reflecting maintained brain volume and preserved cognitive function, as opposed to say something like atrophy that we expect to occur with age.
Were there any sex differences?
We considered sex as an important factor, specifically to understand whether it moderated, or impacted, the effects of cannabis, for two reasons.
One, we know that men and women tend to use cannabis differently, so they have different patterns of use and they report different subjective effects. And two, from the preclinical research there’s evidence that the endocannabinoid system is different in men and women, so the density of cannabinoid receptors differs and there seem to be complex interactions with hormones.
And while there wasn’t a clear-cut or consistent pattern, like male cannabis users always showing more favorable effects than women, we did see significant interactions across several brain regions and cognitive measures, which really suggests that sex is something we need to be looking at because it does seem to be an important factor.
What were the results by cannabis usage category?
We did see that for many of our outcome measures, moderation seemed to be best. For the brain regions and cognitive tests that demonstrated an effect, the moderate-use group generally had larger brain volumes and better cognitive performance.
At the same time, there were a few measures, like volume of the right amygdala and visual memory and learning, where the high use group had the best outcomes.
I think that really suggests that there are dose-dependent effects.
As a caveat, we didn’t have access to detailed information about the patterns of usage, so that would be helpful as additional contextual information.
Did you see any negative effects?
I will say one of the things that was really interesting was that although for almost everything we looked at, there was this positive relationship, there was a single brain region where we saw that higher cannabis use was actually associated with lower brain volume – the posterior cingulate, which is part of the limbic system and is implicated in processes like memory, learning, and emotion.
That said, some research suggests smaller posterior cingulate volume is actually associated with better working memory, so it’s a little unclear what this means. It’s a good reminder that these effects involve multiple processes. It’s not all good or all bad.
Why did you use the UK Biobank?
It’s a huge dataset, providing a great sample of older adults with a lot of awesome health measures important to aging, like neuroimaging and cognitive assessment. It also includes some information on cannabis use, which gave us a really good starting point for our investigation.
Biobanks are a great resource for a small lab like us, because we could never feasibly have a dataset that large. It’s an incredible tool to look at small to moderate effects.
How did the UK Biobank measure cannabis usage, and how did you categorize the data?
In the UK Biobank, people were asked to estimate how many times they’d used cannabis over their lifetime, choosing from a set of ranges. We ended up grouping people into no use, moderate use, and high use, based on the number of times they’d used cannabis. And of course that’s an imperfect way to group people, but it did allow us to approximate dose-dependent effects.
Was there anything that you and the team were surprised by, once you started parsing the data?
Even though preliminary work by our group – and some of our colleagues who have also been focused on older adults – had been seeing these beneficial relationships in older adults using cannabis, I was a little surprised that every cognitive measure that demonstrated a significant effect showed better performance among cannabis users.
It goes against your default assumptions, because I think a lot of research out there has shown cannabis is associated with worse cognitive function, at least acutely.
What do you want people to know about cannabis research?
I think the main takeaway is that the story is nuanced. It’s not a case of cannabis being all good or all bad. I think sometimes people have seen my poster on this project or they see the headline and they say, “Great, I’ll just use more cannabis.”
But it’s more complicated than that. I think it depends on how people are using and what outcomes you’re looking at. What products are being used, for what reasons, and what part of the lifespan are we looking at? Those are important questions and we’re still figuring it out.
For example, I’m interested in the effects of THC versus CBD. We don’t have any of that information in the UK Biobank. Most people in this study were using cannabis quite a while ago, and cannabis at that time looked very different from what’s available today. That context really matters. It’s a complex picture.
Where does your research go next?
We do have another paper under review right now looking at connectivity, or function, of the brain in these same older adults. These data suggest there are also positive impacts of cannabis on the function of these brain regions, not just the size or volume of them, too.
Moving beyond cannabis, we’re also beginning to explore relationships between brain health and psilocybin use.
Why is this research so important?
These substances are often marketed as health-promoting and beneficial to certain populations or for certain conditions, like chronic pain or depression, and we don’t have solid clinical trials to support that or refute that, or how that might look different with aging.
I think it’s a very exciting time where we’re still figuring out what’s going on, and it’s especially important for public health and policy. If people are using these substances, it’s worth knowing what the impacts are, both good and bad.
Key Questions Answered:
A: Not necessarily. While the study found a positive association between moderate use and brain health, it’s not a clinical recommendation. The researchers note that they don’t know the exact potency or type of cannabis used by participants, and “moderate” use was the group with the best results.
A: The adolescent brain is still developing and is highly sensitive to external substances. In older adults, the endocannabinoid system may interact differently with an aging brain, potentially helping to maintain volume and function that would otherwise decline due to atrophy.
A: Most of the benefits were seen in the moderate group. Interestingly, while high users did show the best outcomes in a few specific areas (like the right amygdala and visual memory), the overall trend favored moderation for general brain health and cognition.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this cannabis and brain aging research news
Author: Matthew Hastings
Source: University of Colorado
Contact: Matthew Hastings – University of Colorado
Image: The image is credited to Neuroscience News
Original Research: Closed access.
“Lifetime Cannabis Use Is Associated with Brain Volume and Cognitive Function in Middle-Aged and Older Adults” by Anika Guha, Zening Fu, Vince Calhoun, and Kent E. Hutchison. Journal of Studies on Alcohol and Drugs
DOI:10.15288/jsad.25-00346
Abstract
Lifetime Cannabis Use Is Associated with Brain Volume and Cognitive Function in Middle-Aged and Older Adults
Objective:
Cannabis use has increased among older adults, yet the neurocognitive effects in this demographic remain unclear. Prior work has suggested cannabis may increase brain volume in areas rich in cannabinoid (CB1) receptors, though negative effects are often reported in adolescents.
This study sought to clarify the relationship between cannabis use and brain health among middle-aged and older adults.
Method:
Using data from the UK Biobank, which includes health information from over 500,000 adults, associations between cannabis use, regional brain volume, and cognition in participants aged 40–70 years (mean age = 54.5) were evaluated.
Results:
Lifetime cannabis use was positively associated with regional brain volume in CB1-rich regions, including the caudate, putamen, hippocampus, and amygdala. Greater lifetime use was also linked to better performance in learning, processing speed, and short-term memory.
Individuals reporting use limited to adolescence also showed larger regional volumes and better cognitive performance than non-users. Sex differences in cannabis effects on brain volume and cognition were also observed.
Conclusions:
Results highlight that cannabis may influence brain health differently across the lifespan, potentially offering protective effects in older age while posing risks earlier in development. Protective effects may result from endocannabinoid-mediated modulation of inflammation, immune function, and neurodegeneration.
Observed sex differences likely reflect variation in the endocannabinoid system and underscore the importance of considering sex as a biological variable in studies of cannabis and brain health.
