Scientists reveal cannabis use linked to epigenetic changes: ScienceAlert

A study of more than 1,000 adults suggests that cannabis use may cause genome changes in the human body. The epigenome acts like a set of switches, turning on or off genes to change how our bodies work.

“We observed associations between cumulative marijuana use and multiple epigenetic markers over time,” Lifang Hu, a preventive medicine physician and epidemiologist from Northwestern University Feinberg School of Medicine, explained in July 2023.

Cannabis is a commonly used substance in the United States, with 49% of people having tried it at least once, he and a team of American researchers reported in their published paper. Some US states and other countries have made it legal, but we still don’t fully understand its effects on our health.

The researchers studied about 1,000 adults who participated in a previous long-term study in which they were asked about their cannabis use over a 20-year period. Study participants provided blood samples on two occasions during that period, at 15 and 20 years. They were between 18 and 30 years old at baseline, or “Year 0.”

Using these blood samples taken five years apart, she and her team looked at epigenetic changes, specifically DNA methylation levels, of people who had used cannabis recently or for a long time.

The addition or removal of methyl groups from DNA is one of the most studied epigenetic modifications. Without changing the genomic sequence, it changes the activity of genes, because it is difficult for cells to read the genome’s instruction manual with these molecular changes in their way.

Environmental and lifestyle factors can lead to these methylation changes, which can be passed on to future generations, and blood biomarkers can provide information about recent and historical exposure.

“We previously identified associations between marijuana use and the aging process as captured by DNA methylation,” Hu said.

“We wanted to further explore whether there are specific genetic factors associated with marijuana and whether these factors are associated with health outcomes.”

Comprehensive data on participants’ cannabis use allowed them to estimate cumulative use over time as well as recent use and compare it to DNA methylation markers in their blood for analysis.

They found several DNA methylation markers in blood samples for 15 years, 22 of which were associated with recent use, and 31 of which were associated with cumulative cannabis use. In samples taken at the 20-year point, they identified 132 markers associated with recent use and 16 markers associated with cumulative use.

“Interestingly, we consistently identified one marker that was previously associated with tobacco use, suggesting a possible shared genetic regulation between tobacco and marijuana use,” Ho explained.

Multiple epigenetic changes associated with cannabis use have previously been linked to things such as cellular proliferation, hormone signaling, inflammation, 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.

“This research has 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. Furthermore, studies examining the effect of marijuana on age-related health outcomes may provide further insight into the impact of marijuana on long-term health.”

The study was published in Molecular psychiatry.

A previous version of this article was published in July 2023.