In older adults, cannabis smoking was associated with thousands of epigenetic changes, many in aging and cancer-related pathways, and more than half of these changes persisted in former smokers who had quit.
Epigenetics researchers, pulmonologists, and public health professionals assessing long-term cannabis smoking effects.
5,915 shared gene changes in current and former smokers
What the researchers found
Current cannabis smokers showed 12,115 differentially methylated genes compared to never-smokers, while former cannabis smokers still showed 10,806 differentially methylated genes. Of these, 5,915 genes overlapped between current and former smokers. Fifty enriched pathways were shared between groups, heavily represented by aging and cancer-related pathways.
Why it matters
This is the first study to evaluate whether cannabis smoking cessation reverses epigenetic changes. The finding that most methylation disruptions persist after quitting suggests long-lasting biological effects that may not be undone by simply stopping use.
The numbers in context
N = 93 older adults. Current smokers: 12,115 differentially methylated genes. Former smokers: 10,806. Shared: 5,915 genes. 50 shared enriched pathways, heavily cancer- and aging-related.
How the study worked
Epigenome-wide DNA methylation analysis of peripheral blood from 93 older adults in the Canadian Cohort of Obstructive Lung Disease (CanCOLD), comparing current, former, and never cannabis smokers at FDR < 0.05.
What this study cannot tell us
Very small sample size (n=93) limits statistical power and generalizability. Cross-sectional design cannot track changes over time. Peripheral blood methylation may not reflect tissue-specific effects. Could not fully control for concurrent tobacco use.
How to read the evidence
First-of-its-kind analysis of cessation effects on cannabis-related epigenetic changes, but severely limited by very small sample size.
When this study was published
2025 publication
The bigger picture
While tobacco smoking is well known to cause persistent epigenetic changes linked to disease, this study suggests cannabis smoking may produce similarly durable epigenetic effects. The persistence of changes in former smokers is particularly noteworthy for long-term health risk assessment.
Questions still open
- How long do these methylation changes persist after cessation? Do they eventually reverse with extended abstinence? Are these epigenetic changes functionally linked to cancer or accelerated aging outcomes?
Common questions
Do epigenetic changes from cannabis smoking go away after quitting?
What biological processes were affected?
Read the original research
Cannabis smoking is associated with persistent epigenome-wide disruptions despite smoking cessation.
BMC pulmonary medicine, 25(1), 168
Citation
Cordero, Ana I Hernandez; Li, Xuan; Yang, Chen Xi; Ambalavanan, Amirtha; MacIsaac, Julie L; Kobor, Michael S; Doiron, Dany; Tan, Wan; Bourbeau, Jean; Sin, Don D; Duan, Qingling; Leung, Janice M. (2025). Cannabis smoking is associated with persistent epigenome-wide disruptions despite smoking cessation.. BMC pulmonary medicine, 25(1), 168. https://doi.org/10.1186/s12890-025-03634-9