In UK Biobank data from adults aged 40-70, lifetime cannabis use was associated with larger brain volumes in cannabinoid receptor-rich regions and better performance on learning, processing speed, and memory tests.
Neuroscientists, aging researchers, clinicians counseling older cannabis users, public health communicators
What the researchers found
Using UK Biobank data from participants aged 40-70 (mean age 54.5), lifetime cannabis use was positively associated with regional brain volume in CB1-rich areas including the caudate, putamen, hippocampus, and amygdala. Greater lifetime use was also linked to better performance in learning, processing speed, and short-term memory. Even individuals whose use was limited to adolescence showed larger regional volumes and better cognitive performance than non-users. Sex differences in these associations were observed.
Why it matters
Most cannabis brain research focuses on adolescents and young adults, where findings tend to be negative. This study suggests a more complex picture across the lifespan, where the same substance may have different brain associations at different ages, potentially related to endocannabinoid-mediated neuroprotection.
The numbers in context
UK Biobank sample; ages 40-70; mean age 54.5; positive associations with volume in caudate, putamen, hippocampus, amygdala; better performance in learning, processing speed, short-term memory; effects observed even for adolescence-only users; sex differences present
How the study worked
Cross-sectional analysis of UK Biobank data from adults aged 40-70. Assessed associations between self-reported cannabis use history, regional brain volumes (via MRI), and cognitive performance on validated tasks. Examined sex-specific effects.
What this study cannot tell us
Cross-sectional design cannot determine causation: people with naturally larger brain volumes may be more likely to use cannabis, or other lifestyle factors may explain both. Self-reported use history subject to recall bias. UK Biobank participants tend to be healthier than the general population. Cannot assess cannabis type, potency, or route of administration.
How to read the evidence
Strong: very large population sample (UK Biobank), validated neuroimaging and cognitive measures, though cross-sectional.
When this study was published
2025 publication
The bigger picture
If cannabis use is associated with preserved or enhanced brain volume in aging populations, this challenges the narrative that cannabis is universally harmful to the brain. The proposed mechanism of endocannabinoid-mediated inflammation reduction aligns with emerging research on cannabinoids and neurodegeneration.
Questions still open
- Do these associations reflect a protective effect of cannabis or pre-existing differences in people who choose to use it?
- Would longitudinal data confirm that cannabis use precedes brain volume preservation?
Read the original research
Lifetime Cannabis Use Is Associated with Brain Volume and Cognitive Function in Middle-Aged and Older Adults.
Journal of studies on alcohol and drugs
Citation
Guha, Anika; Fu, Zening; Calhoun, Vince; Hutchison, Kent E. (2025). Lifetime Cannabis Use Is Associated with Brain Volume and Cognitive Function in Middle-Aged and Older Adults.. Journal of studies on alcohol and drugs. https://doi.org/10.15288/jsad.25-00346
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