What we know about cannabis and cancer

Cannabis smoke contains some of the same cancer-causing chemicals found in tobacco smoke, but that does not mean smoking weed causes cancer in the way cigarettes do. The evidence is mixed and incomplete. Some studies suggest a possible link between heavy, long-term cannabis use and certain cancers—particularly lung and throat cancers—while other research finds no clear connection. The difference matters: a possible risk is not the same as a proven one, and the actual danger depends on how much you use, how long you have used it, and the method of use.

The challenge for researchers is that cannabis use patterns vary widely, and most studies cannot prove that weed directly caused a cancer. People who smoke cannabis heavily may also smoke tobacco, live in polluted areas, or have other risk factors. Separating cannabis's effect from everything else is difficult. What we can say is that inhaling any smoke—whether from cannabis, tobacco, or a fire—exposes your lungs to irritants and potentially harmful chemicals.

Key Takeaways

  • Cannabis smoke contains some chemicals known to damage cells, but research has not proven that smoking weed causes cancer the way tobacco does.
  • Heavy, long-term smoking of cannabis may increase the risk of lung and throat cancers, though the evidence remains uncertain and incomplete.
  • Edibles and other non-smoking methods avoid the risks of inhaling smoke but carry their own health considerations.
  • If you use cannabis and are concerned about cancer risk, reducing how much you use or switching to non-smoking methods can lower potential harm.

Why cannabis smoke is a concern

When cannabis burns, it releases tar and other chemicals into your lungs, just as tobacco smoke does. Some of these chemicals—including benzopyrene and nitrosamines—are known to damage DNA in cells. Damaged DNA can sometimes lead to cancer, though the body has repair mechanisms and most damaged cells do not become cancerous.

Cannabis smoke also irritates the airways and lungs. Chronic irritation from any source can increase cancer risk over time. The longer and more heavily you smoke, the more exposure your lungs have to these irritants. This is why researchers have looked most closely at lung and throat cancers in people who smoke cannabis regularly for years.

What the research actually shows

Large studies have not found a clear, definitive link between cannabis use and cancer. A 2019 review by researchers at the University of New South Wales looked at studies published between 1966 and 2018 and found that while some studies suggested a possible increased risk of lung cancer in heavy, long-term users, the overall evidence was weak and inconsistent. Some studies found no link at all.

One reason the evidence is unclear is that most people who smoke cannabis also have other exposures. Many also smoke tobacco. Others have occupational exposures or live in areas with air pollution. Researchers struggle to isolate cannabis as the sole cause. Additionally, cannabis use is often illegal or stigmatized, which means people may not report it accurately in health surveys, making studies less reliable.

For other cancers—such as colorectal, prostate, or breast cancer—the research is even thinner. A few studies have looked at these connections, but the evidence is too limited to draw conclusions.

How method of use changes the risk

Smoking anything—cannabis, tobacco, or other plant material—exposes your lungs to smoke and its chemicals. Vaping heats cannabis to a temperature that releases active compounds without burning the plant, which produces less tar and fewer harmful byproducts than smoking. However, vaping is still relatively new, and long-term health studies are limited.

Edibles and other non-smoking methods (oils, tinctures, capsules) bypass the lungs entirely and avoid the risks of inhaling smoke. They carry different health considerations—such as accidental overdose or liver metabolism—but not the respiratory cancer risk associated with smoking.

If you are concerned about cancer risk and use cannabis, switching from smoking to vaping or edibles can reduce your exposure to smoke-related harm.

Cannabis use and people with cancer

Some people with cancer use cannabis to manage pain, nausea, or loss of appetite during treatment. This is a different question from whether cannabis causes cancer. If you have been diagnosed with cancer and are considering cannabis, talk with your oncologist or cancer care team. They can discuss whether it might help with your specific symptoms and whether it could interact with your treatment.

Cannabis may interact with certain cancer medications or affect how your body processes them. Your care team knows your diagnosis, your treatment plan, and your other medications, so they are the right people to guide this decision.

What you can do to reduce risk

If you use cannabis and want to lower any potential cancer risk, the most direct step is to reduce how much you use or how often you use it. Less exposure to smoke means less exposure to potentially harmful chemicals.

If you smoke cannabis, switching to vaping or edibles removes the smoke exposure entirely. If you continue to smoke, avoiding deep inhalation and holding smoke in your lungs—practices that some people use to intensify the effect—can reduce lung irritation.

If you also smoke tobacco, quitting tobacco should be a priority, since the cancer risk from tobacco is far better established than the risk from cannabis.

Frequently Asked Questions

Does smoking weed cause cancer as much as smoking cigarettes?

No. Tobacco smoke's link to cancer is proven and strong. Cannabis smoke contains some of the same harmful chemicals, but research has not shown that cannabis causes cancer as reliably or as often as tobacco does. That said, any smoke inhaled into the lungs carries some risk.

Is vaping cannabis safer than smoking it?

Vaping avoids the tar and many byproducts of burning plant material, so it likely carries less cancer risk than smoking. However, long-term studies on vaping are limited, so we do not yet know the full picture of its health effects over decades.

Can edibles give you cancer?

Edibles do not expose your lungs to smoke, so they do not carry the respiratory cancer risk of smoking or vaping. They have other health considerations—such as accidental overdose or effects on the liver—but not smoke-related cancer risk.

If I have used cannabis for years, should I get screened for cancer?

Talk with your doctor about your personal risk factors. If you have smoked cannabis heavily for many years, your doctor may recommend lung screening based on your overall health history, smoking habits, and age—not cannabis use alone. Your doctor can advise what makes sense for you.

Does cannabis help treat cancer?

Some people use cannabis to manage cancer symptoms like pain or nausea. Research on cannabis as a cancer treatment itself is very limited. If you have cancer and are interested in cannabis, discuss it with your oncology team, as it may interact with your treatment.