20-year study of 1,000 adults reveals how marijuana alters DNA

Marijuana has intrigued people for decades, especially as more places allow it for medical or recreational use. Many see it as a natural product with relaxing properties, yet scientists have been eager to uncover how it might alter the body in subtle ways.

Researchers tracked the cannabis habits of more than 1,000 U.S. adults over roughly two decades. The team included epidemiologist Lifang Hou from Northwestern University, who analyzed blood samples at two points to search for signs that cannabis use may shift genetic markers.

How marijuana alters DNA

The epigenome includes chemical modifications on DNA that can affect how genes work. These modifications, such as DNA methylation, do not alter the underlying genetic code but can change how active certain sections of DNA are.

Studies have suggested that environmental factors like diet or toxins can impact these epigenetic markers. New findings now propose that cannabis use may leave an imprint, too.

“We observed associations between cumulative marijuana use and multiple epigenetic markers across time,” explained Hou. The markers appeared in people who reported using cannabis in the short term as well as across many years.

While these associations are intriguing, the study does not confirm that cannabis is the direct cause. The researchers emphasize that other behaviors or factors could be partly responsible for the patterns seen in those genetic switches.

Genetic response to cannabis and tobacco

One of the most striking findings was a consistent methylation marker that has already been linked to tobacco use. The same signal appeared in cannabis users, hinting that the body may respond to both substances in a similar way at the genetic level.

This overlap raises questions about whether cannabis and tobacco trigger the same biological pathways or if the presence of smoke itself is responsible for the epigenetic shift.

More studies could help clarify whether these changes stem from the substances themselves or the act of inhalation.

Could these markers predict health risks?

Some of the DNA changes tied to cannabis use were previously linked to conditions like schizophrenia, bipolar disorder, and substance use disorders. While this doesn’t prove a cause-and-effect relationship, it shows a pattern worth paying attention to.

If future research confirms these links, doctors might someday use these markers as early warning signs. They could help flag individuals who may be more vulnerable to certain mental health issues based on their cannabis use history.

Marijuana and DNA methylation

DNA methylation patterns have been linked to a variety of health conditions. Shifting these patterns might change how the body manages cell growth, hormones, and even how it responds to infections.

Scientists have hinted that these modifications could affect neurological processes, too.

Cannabis has long been studied for its possible connections to mental health, so these DNA changes may be relevant to conditions that involve the brain.

Cautious interpretation

“This research has provided novel insights into the association between marijuana use and epigenetic factors,” said epidemiologist Drew Nannini from Northwestern University.

Future research may pinpoint which specific traits or disorders, if any, are most influenced by cannabis-linked epigenetic shifts.

Experts also note that the study relied on self-reported cannabis use. Some participants might have been reluctant to share full details, although confidentiality was maintained to encourage honest responses.

Marijuana use and DNA changes

A substantial segment of U.S. adults, around 49 percent, try marijuana at least once. For frequent or daily users, scientists are interested in whether these epigenetic signs might grow more pronounced over time.

Observing blood samples taken years apart gave the team a way to compare recent users and those who had used cannabis longer. By tracking the same people, they could see how DNA methylation changed along with reported usage levels.

Different effects over time

The number of methylation markers linked to cannabis changed between the two sample points. At year 15, the team found 53 associated markers, while at year 20, that number jumped to 148.

This suggests that some of the epigenetic effects may accumulate with continued use or become more detectable with age. It also opens the possibility that long-term cannabis exposure may affect the body differently than short-term use.

Future research directions

Some experts suggest that more research in different groups is needed to see if these associations appear consistently.

Larger investigations could help determine whether these epigenetic changes are reversible if someone reduces or stops using marijuana.

Many scientists want to see if these markers correlate with specific outcomes, such as mental health shifts or immune function. It may take time to unravel whether the observed epigenetic changes translate into noticeable health effects.

The study is published in the journal Molecular Psychiatry.

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