How Cannabis and Tobacco Affect Brain Volume and Aging

Research from the University of Colorado Anschutz Medical Campus has found that cannabis use among middle-aged and older adults is associated with larger brain volumes and better cognitive function. These findings contrast with previous assumptions regarding the impact of cannabis on the aging brain.

The study, which included authors Anika Guha, Zening Fu, Vince Calhoun, and Kent E. Hutchison, was published in the Journal of Studies on Alcohol and Drugs on December 11, 2025, and made available via PMC on February 11, 2026.

To determine the effects of cannabis use on brain volume and cognitive function, the researchers specifically assessed several covariates, including the age and sex of the participants as well as current substance use, specifically alcohol, and smoking.

Conflicting Research on Brain Volume

The findings from the University of Colorado Anschutz Medical Campus exist alongside other reports that suggest a negative correlation between substance use and brain structure. Reporting from the New York Post and the European Medical Journal has indicated that the use of cannabis and tobacco is linked to reductions in brain volume.

Some data suggests a distinction between the two substances, with reports from News-Medical indicating that smoking tobacco shrinks key brain regions while cannabis demonstrates weaker effects on brain volume.

Methodological Limitations

The discrepancy between these findings highlights the complexity of studying substance use and neurology. According to a review published in Wiley Online Library, much of the existing literature assessing cannabis and tobacco use in relation to brain volume is cross-sectional.

The cross-sectional nature of these studies limits the ability of researchers to make causal inferences. This means that while associations between substance use and brain volume can be identified, This proves difficult to definitively prove that the substances caused the observed changes in brain structure.