Lifetime Cannabis Use Linked to Larger Brain Volumes and Better Cognition in Middle-Aged and Older Adults

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.

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.

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.

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.

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.