Summary: New research reports a surprising association between lifetime cannabis use and markers of brain health in middle-aged and older adults. In an analysis of roughly 26,000 participants from the UK Biobank (participants approximately ages 40–77, mean age about 55), researchers observed that lifetime cannabis use was generally linked with larger regional brain volumes in specific areas and with better performance on a range of cognitive tests.
These findings contrast with much of the literature on adolescents, where heavy cannabis use is often associated with impaired cognitive development. Older adults in this study—many of whom use cannabis for sleep or chronic pain—showed preserved volume in regions critical for memory and learning, such as the hippocampus. The results point to a complex, age-dependent relationship between cannabis and brain health, with a “moderate” pattern of lifetime use showing the most consistent positive associations.
Key facts
- Preserved regional volume: Lifetime cannabis users tended to have larger volumes in brain regions that are rich in CB1 cannabinoid receptors, including the hippocampus, caudate, putamen, and amygdala.
- Better cognitive performance: Cannabis-exposed participants performed better on measures of learning, memory, processing speed, attention, and executive function in this sample.
- Moderation appears important: The most consistent positive associations were found in the moderate-use group, suggesting a dose-dependent pattern rather than a strictly linear benefit with increasing use.
- Regional nuance: Not every region showed a positive relationship—higher lifetime use was associated with smaller volume in the posterior cingulate for this sample, a reminder that effects can be region-specific and complex.
- Demographic relevance: The study highlights a growing population of older adults who use cannabis for therapeutic reasons and who have been underrepresented in cannabis research compared with younger users.
Source: University of Colorado
This population-level study was led by researchers at CU Anschutz and used the UK Biobank to examine how lifetime cannabis exposure relates to brain anatomy and cognitive function in later life. As Anika Guha, PhD, a clinical psychologist and faculty research associate in the Department of Psychiatry at CU Anschutz, notes, more older adults now use cannabis, often for sleep or chronic pain, and this raises important questions about long-term effects as people live longer.
Guha and colleagues emphasize that these results are observational and that key details about the cannabis products used—such as potency, THC versus CBD composition, and exact usage patterns—were not available. Still, the size and scope of the dataset allowed the team to detect small-to-moderate associations between lifetime use and multiple neurocognitive outcomes.
Findings in plain language
The study examined specific brain regions rather than overall brain volume, focusing on areas with high CB1 receptor density. The hippocampus, a region critical for memory that typically declines with aging and in dementia, was one of the regions showing larger volume among people with a history of cannabis use. In general, larger regional volumes correlated with better cognitive test scores in this cohort, which suggests that these volumetric differences may reflect preserved brain structure and function rather than unhealthy enlargement.
The investigators categorized lifetime cannabis exposure into groups (no use, moderate use, high use) based on self-reported lifetime frequency. For many outcomes the moderate group showed the strongest positive associations, though a few measures (for example, right amygdala volume and some visual memory tasks) showed the best outcomes in the high-use group. These patterns point to dose-dependent and region-specific effects that merit further study.
Sex differences and complexity
The team treated sex as an important biological variable because men and women tend to use cannabis differently and because preclinical work suggests the endocannabinoid system and CB1 receptor distribution vary by sex and may interact with hormones. While the study did not reveal a uniform pattern favoring one sex, there were significant interactions between sex, brain measures, and cognition across several outcomes, indicating sex may modulate cannabis–brain relationships.
Any negative signals?
Yes. The posterior cingulate—a limbic region involved in memory, learning, and emotion—showed smaller volume with higher lifetime cannabis exposure in this sample. Interpretation is not straightforward: some prior work links smaller posterior cingulate volume with particular cognitive differences, so this finding underscores the mixed and region-specific nature of the results.
Why use the UK Biobank?
The UK Biobank provides a large, well-characterized sample of older adults with neuroimaging and cognitive measures, which allows researchers to investigate associations that would be difficult to detect in smaller cohorts. The dataset includes self-reported lifetime cannabis use, enabling an initial population-level look at long-term relationships between cannabis, brain structure, and cognition.
Key questions answered
Q: Should people start using cannabis to prevent dementia?
A: Not as a clinical recommendation. The study reports associations, not causal effects. The best outcomes were seen in the moderate-use group, and important details about product potency and composition were not available.
Q: Why do older adults show different results than adolescents?
A: The adolescent brain is still developing and is particularly sensitive to external substances. In older adults, interactions between the aging brain and the endocannabinoid system may produce different effects, potentially helping to preserve volume and function that otherwise decline with age.
Q: Is high use as beneficial as moderate use?
A: Generally no. Most positive associations were strongest in the moderate-use group, although some specific measures favored high users. Overall, the findings favor moderation rather than heavier lifetime exposure for general cognitive and structural outcomes in this dataset.
Editorial notes
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by staff.
About this cannabis and brain aging research news
Author: Matthew Hastings
Source: University of Colorado
Contact: Matthew Hastings – University of Colorado
Image: Image credited to Neuroscience News
Original research: Lifetime Cannabis Use Is Associated with Brain Volume and Cognitive Function in Middle-Aged and Older Adults. Authors: Anika Guha, Zening Fu, Vince Calhoun, and Kent E. Hutchison. Journal of Studies on Alcohol and Drugs. DOI: 10.15288/jsad.25-00346. (Closed access)
Abstract
Objective: Cannabis use has grown among older adults, yet its neurocognitive effects in this demographic remain unclear. Prior studies often report negative effects in adolescents, while some work suggests cannabis may increase volume in CB1-rich brain regions. This study aimed to clarify how lifetime cannabis use relates to brain structure and cognition in middle-aged and older adults.
Method: Using UK Biobank data, the researchers evaluated associations between self-reported lifetime cannabis use, regional brain volumes, and cognitive performance in a large sample of adults in midlife and older age (approximately ages 40–77).
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 also correlated with better performance on measures of learning, processing speed, and short-term memory. Individuals who reported use limited to adolescence also showed larger regional volumes and better cognitive outcomes than non-users in this dataset. Sex differences were observed in several brain and cognitive measures.
Conclusions: These results suggest the relationship between cannabis and brain health varies across the lifespan: cannabis exposure may associate with preserved brain volume and cognitive performance in middle-aged and older adults, while risks are more consistently reported for younger users. Potential mechanisms include endocannabinoid-mediated modulation of inflammation, immune function, and neurodegenerative processes. Observed sex differences highlight the importance of considering sex as a biological variable in future cannabis and brain health research.