in 2023 A published study of more than 1,000 adults suggests that cannabis use can leave lasting fingerprints on the human body, not in our DNA code itself, but in the expression of that code.
US scientists have found that this can cause changes in the epigenome, which acts as a set of switches that activate or deactivate genes related to the functioning of our body; findings confirmed by a systematic review of the literature, which in 2024 published by Portuguese scientists.
“We observed associations between cumulative marijuana use and several epigenetic markers over time,” epidemiologist Lifang Hou of Northwestern University explained his team’s findings in 2023.
Related: Cannabis can leave a distinct mark on your DNA, study finds
Cannabis is a widely 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 US states and other countries have legalized the use of cannabis, but we still don’t fully understand its effects on our health.
To investigate this, researchers analyzed data from the Longitudinal Health Study, which followed about 1,000 adults over two decades.
Participants, who were between 18 and 30 years old at the start of the study, were asked about their cannabis use over the years and gave blood samples at ages 15 and 20.
Using these blood samples from five years apart, Hou and her team examined epigenetic changes, particularly DNA methylation levels, in people who had recently or had used cannabis for a long time.
The addition or removal of methyl groups from DNA is one of the most studied epigenetic modifications.
When epigenetic factors, which can come from other genes or the environment inside or outside the cell, recruit a methyl group, it changes the expression of our genes. (ttsz/iStock/Getty Images)
Without changing the genomic sequence, DNA methylation affects how easily cells “read” and interpret genes, much like someone covers up the basic lines of your instruction set.
Environmental and lifestyle factors can cause these methylation changes, which can be passed on to future generations, and blood biomarkers can provide information about recent and historical exposure.
“We previously found links between marijuana use and the aging process through DNA methylation,” Hou said.
“We wanted to further investigate whether specific epigenetic factors were associated with marijuana and whether these factors were associated with health outcomes.”
Detailed data on participants’ cannabis use allowed the researchers to measure total use over time, as well as recent use, and compare it to DNA methylation markers in their blood for analysis.
In 15 years of blood samples, they found a large number of DNA methylation markers, 22 of which were associated with recent use and 31 with cumulative cannabis use.
In samples taken over 20 years, they identified 132 markers associated with recent use and 16 associated with cumulative use.
“Interestingly, we consistently found one marker previously associated with tobacco use,” Hou explained, “which suggests a possible shared epigenetic regulation between tobacco and marijuana use.”
Several epigenetic changes associated with cannabis use have previously been linked to things like cell proliferation, hormone signaling, infections, neurological disorders such as schizophrenia and bipolar disorder, and substance use disorders.
It is important to note that this study does not prove that cannabis directly causes these changes or causes health problems.
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“This study provided new insights into the relationship between marijuana use and epigenetic factors,” said epidemiologist Drew Nannini of Northwestern University.
“Additional studies are needed to determine whether these associations are consistently observed in different populations. Additionally, studies examining the effects of marijuana on age-related health outcomes may provide more information about the long-term health effects of marijuana.”
The study was published in Molecular psychiatry.
An earlier version of this article was published in 2023. in July