Cannabis use may cause changes in the human body’s epigenome, according to a study of over 1,000 adults. The epigenome acts like a series of switches, activating or deactivating genes to change the way our bodies function.
“We observed associations between cumulative marijuana use and multiple epigenetic markers over time,” say Lifang Hou, a preventive medicine physician and epidemiologist from Northwestern University’s Feinberg School of Medicine.
Cannabis is a commonly used substance in the United States, with 49 percent of people trying it at least once, Hou and a team of US researchers report in their published paper. Some US states and other countries have legalized it, but we still don’t fully understand the impact it has on our health.
The researchers studied about 1,000 adults who had participated in a previous long-term study in which they were asked about their cannabis use over a period of 20 years. Study participants provided blood samples twice during that time, at the 15 and 20 year points. They were aged between 18 and 30 years at baseline, or ‘year 0’.
Using these blood samples from five years apart, Hou and her team looked at the epigenetic changes, specifically DNA methylation levels, people who have used cannabis recently or for a long time.
Add or subtract methyl groups from DNA is one of the most studied epigenetic modifications. Without changing the genomic order, it changes the activity of the genes, because it is more difficult for cells to read the genome instruction manual with these molecular changes in their way.
Environmental and lifestyle factors can trigger these methylation changes, which can be passed on to future generations, and blood biomarkers it can provide information about both new and historical exposures.
“We previously identified associations between marijuana use and the aging process as captured by DNA methylation,” Hou say.
“We wanted to further explore whether specific epigenetic factors were associated with marijuana and whether these factors are associated with health outcomes.”
The comprehensive data on participants’ cannabis use allowed them to assess cumulative use over time as well as recent use and compare it to DNA methylation markers in their blood for analysis.
They found multiple DNA methylation markers in the 15-year blood samples, 22 related to recent use, and 31 related to cumulative use of cannabis. In the samples taken at the 20-year point they identified 132 marks related to recent use and 16 related to cumulative use.
“Interestingly, we consistently identified one marker that was associated with previous tobacco use,” Hou explains“suggesting possible shared epigenetic regulation between tobacco and marijuana use.”
Multiple epigenetic changes associated with cannabis use have previously been linked to things like cellular proliferation, hormone signalinginfections, neurological disorders such as schizophrenia and bipolar disorderand substance use disorders.
It is important to note that this study does not prove that cannabis directly causes these changes or that it causes health problems.
“This research has provided new insights into the relationship between marijuana use and epigenetic factors,” say epidemiologist Drew Nannini of Northwestern University.
“Additional studies are needed to determine whether these associations are observed consistently in different populations. Furthermore, studies examining the effect of marijuana on age-related health outcomes may provide additional insight into the long-term effect of marijuana on health.”
The study is published in Molecular Psychiatry.