Marijuana, also known as cannabis, is becoming more widely used across the United States as more states make it legal. In 2019, nearly 48 million Americans—about 18% of the population—said they had used marijuana, according to the Centers for Disease Control and Prevention (CDC).
People smoke it in rolled joints or bongs, brew it into tea, or mix it into food. As marijuana use becomes more common, scientists are trying to understand what it really does to our bodies over time.
A recent study by researchers at Northwestern Medicine takes a closer look at how marijuana might affect our DNA. While marijuana is often seen as harmless—or even helpful for some medical conditions—this new research suggests that the story might be more complicated, especially when it comes to how it may change activity in our genes.
The study was led by Dr. Lifang Hou, a cancer researcher. Her team studied blood samples from more than 900 adults who had taken part in a long-term heart health study. Each person had given blood twice—five years apart.
The researchers asked them about their marijuana use during that time, including how often they used it and how much they had used in their lifetime.
Then, they looked at the participants’ DNA to see if anything had changed. They found something called DNA methylation, which is when small chemical tags attach to certain parts of your DNA.
These tags don’t change the DNA itself, but they can turn certain genes on or off—kind of like flipping a light switch. This can affect how your body grows, fights infections, or responds to stress.
The researchers found 16 to 132 genetic markers that seemed to be linked to marijuana use. These markers were located in parts of the DNA that control things like how cells grow, how hormones work, and how the immune system functions.
Interestingly, some of these changes were in areas connected to mental health conditions such as schizophrenia, bipolar disorder, and substance use problems.
It’s important to understand that this study does not prove that marijuana use causes these DNA changes. It only shows that there is a link worth exploring further. We still don’t know if these changes are harmful or if they go away over time.
The study doesn’t answer whether marijuana causes mental health conditions or increases the risk of diseases—it simply raises new questions.
Still, this research matters because it adds to our understanding of how marijuana might affect the body in ways we can’t easily see. If using marijuana changes the way certain genes behave, even slightly, those changes could have long-term effects on health—especially when combined with other risk factors like genetics, age, or lifestyle.
The study also suggests we need more research on how marijuana affects different groups of people. For example, does the impact on DNA look different for men and women? Do people with certain genetic traits respond differently? And what happens to these changes over many years?
As marijuana becomes easier to get and more people use it for medical or recreational reasons, it’s important to weigh both the benefits and the risks. Some studies show marijuana might help reduce depression, improve quality of life, or protect brain health in older adults. But this new research reminds us that there may also be risks we don’t fully understand yet.
The study was published in Molecular Psychiatry, and it is one of the first to link marijuana use with changes in how genes may function. While there’s still a lot to learn, it’s a step toward understanding the full picture of how marijuana affects our health—not just in the short term, but possibly at the molecular level too.
In the end, this research shows that marijuana is not risk-free. Whether you use it or not, staying informed and aware of new scientific findings can help you make smarter, healthier decisions.
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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