Cannabis use linked to epigenetic changes, study finds: ScienceAlert

A study of over 1,000 adults suggests that cannabis consumption can lead to changes in the human body’s epigenome. The epigenome works like a series of switches that turn genes on or off to change how our bodies function.

“We observed associations between cumulative marijuana use and multiple epigenetic markers over time,” explained Northwestern University epidemiologist Lifang Hou when the research was published in 2023.

Cannabis is a commonly used substance in the United States, with 49 percent of people having tried it at least once, Hou and a team of U.S. researchers report in their published paper.

Some US states and other countries have legalized cannabis, but we still don’t fully understand its effects on our health.

Researchers looked at around 1,000 adults who had taken part in a previous long-term study in which they were asked about their cannabis use over a 20-year period.

The study participants provided blood samples twice during this period, at ages 15 and 20. They were between 18 and 30 years old at the start of the study, “year 0”.

Using these blood samples from a five-year period, Hou and her team examined epigenetic changes, particularly DNA methylation levels, in people who had recently or long-term cannabis use.

Adding or removing methyl groups from DNA is one of the most studied epigenetic modifications. Without changing the genome sequence, the activity of genes changes because it is more difficult for cells to read the genome’s instruction manual when these molecular changes are on their way.

Environmental and lifestyle factors can trigger these methylation changes, which can be passed on to future generations, and blood biomarkers can provide information about current and historical exposures.

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

“We wanted to further investigate whether specific epigenetic factors are associated with marijuana and whether these factors are associated with health outcomes.”

The 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 numerous DNA methylation markers in the 15-year blood samples, 22 of which were related to recent use and 31 related to cumulative cannabis use. In samples taken after 20 years, they identified 132 markers that were associated with recent use and 16 that were associated with cumulative use.

“Interestingly, we consistently identified a marker that has previously been associated with tobacco use,” Hou explained, “suggesting 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.

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

“Additional studies are needed to determine whether these associations are consistently observed across different populations. “In addition, studies examining the effects of marijuana on age-related health outcomes may provide further insight into the long-term effects of marijuana on health.”

The study was published in Molecular Psychiatry.

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