The use of cannabis can leave permanent fingerprints on the human body, a study of more than a thousand adults published in 2023 suggests – not in our DNA code itself, but in how that code is expressed.
US researchers have found that it can cause changes in the epigenome, which acts as a set of switches that activate or deactivate the genes involved in how our bodies work; The findings were confirmed by a systematic literature review published in 2024 by investigators in Portugal.
“We have seen associations between the use of marijuana and a lot of epigenetic markings over time,” Epidemiologist LifAng Hou from Northwestern University explained the findings of his group in 2023.
Related: Cannabis can leave a unique mark on your DNA, study reveals
Cannabis is a commonly used substance in the US, with nearly half of Americans having tried it at least once, Hou and team report in their published paper.
Some people in the US and other countries have used legal cannabis, but we still don’t fully understand its effects on our health.
To investigate this, researchers analyzed data from a long-term health study that followed 1,000 adults for more than two decades.
The participants, who were between the ages of 18 and 30 when the study began, were assessed on their cannabis use over the years and provided blood samples at 15 and 20 years.
Using these blood samples from five different years, his team looks at epigenetic changes, especially DNA methylation levels, of people who have used marijuana recently or for a long time.
The addition or removal of methyl groups from DNA is one of the most studied epigenetic mechanisms.
When epigenetic factors, which can come from other genes or the environment inside the cell or more, to hire a methyl group, it changes the expression of our genes. (TTSz / istock / Getty Images)
In addition to changing the genomic sequence, DNA methylation affects cells easily and translates genes, like a person who covers important lines in your set of instructions.
Environmental factors and lifestyles can cause these methylation changes, which can be passed on to future generations, and blood tests can provide information about recent and historical exposure.
“We identified an association between marijuana use and the aging process as captured by DNA methylation,” Hou said.
“We wanted to further examine whether certain epigenetic factors were associated with marijuana and whether these factors were related to health outcomes.”
Comprehensive data on participants’ cannabis use allows researchers to measure cumulative use over time and recent use and compare it to DNA methylation markers in their blood for analysis.
They found multiple DNA methylation markers in 15 annual blood samples, 22 associated with recent use, and 31 associated with active cannabis use.
On hands taken at the 20-year mark, they identified 132 marks linked to recent use and 16 linked to cold use.
“It is interesting that we have identified one marker that has been associated with previous tobacco use,” Hous explained, “suggesting that there are shared epigenetic principles between tobacco and marijuana use.”
Many of the epigenetic changes associated with prior cannabis use have been linked to factors such as cellular metabolism, hormone signaling, infection, mood disorders, and developmental disorders.
It is important to note that this study does not prove that marijuana directly causes these changes or causes health problems.
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“This study provided a novel understanding of the interface between marijuana use and epigenetic factors,” said epigemiologist Drew at Northwestern University.
“Further research is needed to determine whether these associations are consistent across populations.
The study was published internally Molecular Psychiatry.
An earlier version of this article was published in July 2023.
