Cannabis Use May Leave Lasting Epigenetic Fingerprints on the Human Body

Cannabis consumption may leave enduring marks on the human body, according to a 2023 study involving more than 1,000 adults. The changes are not to the DNA sequence itself, but rather to the way that genetic code is expressed.

Researchers in the US reported that cannabis could alter the epigenome, a system of switches that turns genes involved in bodily functions on or off. These findings were supported by a systematic literature review published in 2024 by Portuguese researchers.

"We observed associations between cumulative marijuana use and multiple epigenetic markers across time," epidemiologist Lifang Hou from Northwestern University explained in 2023.

Cannabis use and epigenetic changes

Cannabis is widely used in the US: nearly half of Americans have tried it at least once, according to Hou and her colleagues' published paper.

Although cannabis use has been legalised in some US states and other nations, its health effects remain incompletely understood.

To examine the issue, the team assessed information from a long-term health study that followed roughly 1,000 adults for two decades. The participants were aged between 18 and 30 when the research started. Over the years, they completed surveys about their cannabis use and supplied blood samples after 15 and 20 years.

Using samples collected five years apart, Hou and her colleagues examined epigenetic alterations in people who had used cannabis recently or over a prolonged period. More specifically, they assessed DNA methylation levels.

Adding or removing methyl groups from DNA is among the most extensively studied forms of epigenetic modification. DNA methylation does not alter the genomic sequence, but it can influence how readily cells ‘read’ and interpret genes - rather like obscuring crucial lines in a set of instructions.

Environmental and lifestyle influences can prompt these methylation changes. They may be passed on to future generations, while blood biomarkers can offer information on both recent and past exposures.

"We previously identified associations between marijuana use and the aging process as captured through DNA methylation," Hou said.

"We wanted to further explore whether specific epigenetic factors were associated with marijuana and whether these factors are related to health outcomes."

DNA methylation markers linked with cannabis use

The detailed records of participants’ cannabis use enabled the researchers to calculate both cumulative consumption over time and recent use, then compare these measures with DNA methylation markers found in blood.

In blood samples obtained at year 15, the researchers detected numerous DNA methylation markers: 22 were linked with recent use and 31 with cumulative cannabis use.

At the 20-year collection point, they found 132 markers associated with recent use, alongside 16 related to cumulative use.

"Interestingly, we consistently identified one marker that has previously been associated with tobacco use," Hou explained, "suggesting a potential shared epigenetic regulation between tobacco and marijuana use."

Several epigenetic changes associated with cannabis use had already been connected with cellular proliferation, hormone signalling, infections, neurological conditions including schizophrenia and bipolar disorder, and substance use disorders.

Crucially, the study does not demonstrate that cannabis directly produces these changes or leads to health problems.

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

"Additional studies are needed to determine whether these associations are consistently observed in different populations. Moreover, studies examining the effect of marijuana on age-related health outcomes may provide further insight into the long-term effect of marijuana on health."

The study was published in Molecular Psychiatry.

An earlier version of this article was published in July 2023.