A new study has revealed that cannabis use may cause long-lasting changes to human DNA, even after a person quits. The research, published in BMC Pulmonary Medicine, found that smoking marijuana affects over 10,000 genes, many of which are linked to brain function, aging, and cancer.
Epigenetic Alterations: More Than Just Temporary Damage
The study focused on the epigenome—chemical tags that sit atop our DNA and regulate how genes are turned on or off. These epigenetic changes do not alter the DNA sequence itself but can have lasting biological consequences.
Researchers examined blood samples from 1,000 adults enrolled in a U.S.-based epidemiological study. They compared individuals who smoked marijuana regularly but did not use tobacco with those who had never smoked either substance.
The results were clear: cannabis exposure led to widespread changes in DNA methylation patterns, a key type of epigenetic modification. Over 10,000 gene sites were affected, and these genes were predominantly involved in critical pathways like synaptic signaling (important for brain communication), immune system response, hormone regulation, and cellular aging.
Damage Persists After Quitting
Perhaps most strikingly, the research indicated that even after users stopped consuming cannabis and adopted healthier lifestyles, many of these genetic changes remained. The residual effects were still measurable, suggesting a lasting biological imprint from marijuana use.
This contrasts with tobacco-related epigenetic damage, which has been studied for decades. While some methylation changes caused by tobacco use have been shown to fade over time after cessation, cannabis-related changes appear to linger longer—though further long-term studies are needed to confirm this.
Why This Matters for Public Health
As marijuana becomes legal in more U.S. states and its use becomes increasingly normalized, this study adds an important layer to the public health conversation. While cannabis is often viewed as less harmful than tobacco or alcohol, the findings suggest that its long-term biological impact may be more significant than previously understood.
The altered genes identified in the study were associated with a range of conditions, including neurodegenerative diseases, psychiatric disorders, and various cancers. Though the study does not claim that marijuana directly causes these illnesses, it highlights how cannabis may contribute to biological pathways that increase risk.
Calls for Further Research
Experts urge caution in interpreting the findings. The study was observational and cannot prove causation. However, it opens the door for more comprehensive research on the long-term epigenetic effects of cannabis—especially as recreational use continues to rise across the U.S.
The researchers noted the need to expand their study population and examine more tissue types beyond blood. The brain, in particular, may reveal even more significant changes given cannabis’s psychoactive properties and its interaction with the endocannabinoid system.
Implications for Policy and Awareness
This study may influence future guidelines on cannabis use, particularly for adolescents and young adults whose brains are still developing. It also underlines the importance of educating users about the potential long-term biological effects of marijuana, especially in light of increasing potency in modern cannabis strains.
As science continues to catch up with policy, findings like these serve as a reminder that “natural” or “legal” does not always mean risk-free.
