Cannabis use might leave behind notable traces on the human body, as indicated by a 2023 study involving over 1,000 adults. Interestingly, these changes are not in our DNA sequence but rather in the way it’s expressed.
Researchers from the U.S. discovered potential alterations in the epigenome. This epigenome acts like a switchboard that manages the activation or deactivation of genes crucial for our bodily functions. The findings were also supported by a comprehensive review conducted by Portuguese researchers in 2024.
“We noted associations between the amount of marijuana used over time and various epigenetic markers,” stated epidemiologist Lifang Hou from Northwestern University regarding the team’s 2023 findings.
Related: Cannabis Can Leave a Distinct Mark on Your DNA, Study Reveals
Cannabis is widely used in the U.S., with nearly half the population having tried it at least once, as reported in the team’s paper.
While several U.S. states and other nations have legalized cannabis, the complete effects on health remain somewhat unclear.
To delve deeper, the research team analyzed data from a long-term health study following around 1,000 adults for two decades.
The participants, aged 18 to 30 when the study started, reported their cannabis use over the years and provided blood samples at the 15- and 20-year intervals.
With these blood samples from five years apart, Hou’s team investigated the epigenetic changes, notably the DNA methylation levels, in people who had recently used cannabis or had a long history of use.
The addition or removal of methyl groups from DNA is a well-explored epigenetic modification.
Differentiating the genomic sequence itself, DNA methylation influences the efficiency with which cells ‘read’ and interpret genetic instructions. It’s a bit like covering critical lines in a set of guidelines.
Both environmental and lifestyle factors can instigate these methylation changes. There’s even a possibility that they might be passed down through generations. Blood biomarkers can reveal insights into both recent and past exposures.
“In earlier work, we had identified links between marijuana use and the aging process, measured through DNA methylation,” Hou remarked.
“We aimed to dig deeper into whether certain epigenetic factors were specifically correlated with marijuana and if these are connected to health outcomes.”
The comprehensive data on cannabis use from participants enabled the team to gauge both cumulative and recent exposure, allowing comparisons with their DNA methylation markers.
The analysis revealed multiple DNA methylation markers from the 15-year blood samples—22 tied to recent use and 31 linked to cumulative use.
For the samples taken after 20 years, there were 132 markers associated with recent use and 16 related to cumulative cannabis usage.
“Interestingly, we continually found a specific marker that’s also been associated with tobacco use,” Hou noted, hinting at possible shared epigenetic regulation between the two substances.
Various epigenetic changes tied to cannabis use had previously been connected with aspects like cellular proliferation, hormonal signaling, and conditions such as schizophrenia, bipolar disorder, and substance use disorders.
It’s worth mentioning that this study doesn’t imply a direct causation between cannabis usage and these changes or related health issues.
“This investigation has offered new perspectives on the relationship between marijuana use and epigenetic factors,” commented epidemiologist Drew Nannini from Northwestern University.
“More research is necessary to see if these associations are consistently recognized across diverse populations. Additionally, studies focusing on marijuana’s effects on age-related health outcomes could shed light on long-term health implications.”
The findings are published in Molecular Psychiatry.
An earlier version of this article appeared in July 2023.
