20-Year Study Examines How Marijuana Use Affects DNA and Epigenetics

Marijuana has intrigued people for decades, particularly as its legal status evolves in various regions for medical and recreational use, Earth.com reports.

Many see it as a natural product with relaxing properties, but scientists have long sought to understand its potential effects on the body, especially in subtle ways. A new 20-year study of over 1,000 US adults offers fresh insights into how cannabis use may influence the genetic markers in our bodies.

The research, led by epidemiologist Lifang Hou of Northwestern University, analyzed blood samples from participants at two different points in time. The goal was to examine potential shifts in epigenetic markers, which are chemical modifications on DNA that can influence gene activity without changing the underlying genetic code.

The study suggests that marijuana use might cause changes in the epigenome, the system that regulates gene expression. These changes, particularly in DNA methylation—the process of adding methyl groups to DNA—can affect how genes are activated or deactivated. Though the underlying genetic sequence remains unchanged, the activity of certain genes may be altered, potentially influencing bodily functions.

While the findings show a correlation between cannabis use and several epigenetic markers, the study does not confirm causality. Researchers caution that other factors or behaviors might contribute to these changes, and further studies will be needed to establish a direct link between cannabis and genetic alterations.

One of the more striking discoveries was the presence of a methylation marker in cannabis users that is also commonly associated with tobacco use. This suggests that cannabis and tobacco may trigger similar biological pathways or, alternatively, that the act of inhaling smoke from both substances could be responsible for the observed epigenetic shifts.

The overlap between cannabis and tobacco is intriguing but still requires more research to determine whether the substances themselves or the inhalation process are the main factors at play.

The study found that some of the DNA changes linked to marijuana use have been previously associated with mental health conditions such as schizophrenia, bipolar disorder, and substance use disorders. While these findings do not establish a cause-and-effect relationship, they do highlight a pattern that warrants further exploration.

If future research confirms these connections, doctors could potentially use these markers as early indicators of mental health vulnerabilities in individuals with a history of cannabis use. These findings may also help healthcare professionals better understand how marijuana interacts with the body’s neurological processes.

DNA methylation is known to play a role in various health conditions by influencing cell growth, hormone regulation, and immune function. Some scientists suggest that these epigenetic changes could even affect brain function, making them particularly relevant for conditions involving mental health.

While the study provides valuable insights into the potential links between marijuana use and epigenetic changes, experts urge cautious interpretation. Drew Nannini, a co-author of the study, noted that future research will need to confirm which specific conditions or traits, if any, are most influenced by these shifts.

Additionally, the study relied on self-reported marijuana use, which can sometimes be inaccurate. Although confidentiality was maintained to encourage honest participation, there is a possibility that some participants were reluctant to fully disclose their cannabis use.

The study observed DNA methylation changes over a period of 20 years, comparing those who used cannabis in the short term with long-term users. The results showed that the number of methylation markers associated with cannabis use increased over time, suggesting that the effects of cannabis on the epigenome may accumulate with prolonged use.

At the 15-year mark, 53 markers were identified, while at the 20-year point, this number had increased to 148. These findings indicate that long-term cannabis use might have more pronounced or detectable epigenetic effects compared to short-term use.

Researchers emphasize that larger, more diverse studies are needed to confirm whether the observed epigenetic changes are consistent across different groups. Additionally, further investigations could explore whether these changes are reversible if individuals reduce or stop using marijuana.

Some scientists are also interested in examining whether these epigenetic markers correlate with specific health outcomes, such as shifts in mental health or immune function. It may take years to fully understand whether these changes translate into meaningful health effects.

The study was published in the journal Molecular Psychiatry.