Marijuana is becoming more accepted and widely used across the United States. About 18% of Americans — nearly 1 in 5 — have tried it, and in 2019, nearly 48.2 million people used it in some form.
Whether smoked in joints or bongs, brewed in tea, or mixed into food, marijuana is now the most commonly used drug in the country, according to the Centers for Disease Control and Prevention (CDC).
Even as marijuana becomes more legal and popular, scientists still don’t fully understand what it does to the body over time. That’s why a team from Northwestern Medicine led by Dr. Lifang Hou decided to investigate its possible effects at a deeper level — inside our DNA.
Studying the Effects of Marijuana Use on DNA
The researchers looked at blood samples from more than 900 adults. These samples had been collected as part of a larger heart health study, with blood drawn five years apart. Participants were asked how often they used marijuana and how much they had used over their lifetimes.
The team then studied their DNA to look for a process called DNA methylation — a natural chemical change where tiny molecules attach to DNA and can switch certain genes on or off. These changes don’t rewrite your genes, but they can affect how your genes work.
What They Discovered
The researchers found that marijuana use was linked to clear changes in DNA methylation. In fact, they discovered between 16 and 132 DNA markers connected to marijuana use, depending on how heavily a person had used the drug.
Many of these changes were found in parts of the DNA related to:
- Cell growth
- Hormone activity
- Immune system responses
- Mental health conditions like schizophrenia, bipolar disorder, and substance use problems
While these findings don’t prove that marijuana causes health problems, they suggest there may be long-term biological effects — even at the genetic level — from regular marijuana use.
Why It Matters
This study doesn’t show that marijuana use directly causes disease. It’s also unclear if these DNA changes lead to health issues later in life. However, the fact that there’s a measurable connection between marijuana use and changes in the body’s genetic activity is important.
Scientists see this as a starting point. It’s a signal that more research is needed, especially to understand how these changes might impact long-term health — including risks for mental illness or chronic conditions. It may also help explain why marijuana affects people in different ways.
A Call for Continued Research
As marijuana use becomes more common and socially accepted, studies like this one can help doctors and the public better understand its potential risks and benefits. Research in this area can guide safer use, help shape public policy, and support individuals who may be at risk of negative effects.
In short, this new research offers a peek into what marijuana might be doing at a microscopic level. It doesn’t answer all the questions — but it’s an important clue in the bigger picture of marijuana and health.
The study was published in Molecular Psychiatry. As with all new science, it’s only one piece of the puzzle, but it adds to our growing understanding of how lifestyle choices like cannabis use might shape our health — even down to our genes.
If you care about cannabis, please read studies that what you need to know about cannabis and heart attack, and CBD from cannabis may help inhibit COVID-19 infection.
For more information about cannabis, please see recent studies that medical cannabis could help reduce depression, and results showing this stuff in cannabis may protect aging brain, treat Alzheimer’s.
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