Marijuana (Cannabis) Smoking and Cancer Risk

Marijuana (cannabis) smoke has many of the same cancer-causing agents (carcinogens) as tobacco but in higher amounts. This raises the concern that smoking marijuana may be a risk factor for cancer. Studies are hard to do because some people may not be truthful about their use of marijuana. It is hard to know how often marijuana is used and the amount of exposure over many years. In addition, many people who use marijuana also smoke tobacco.

Marijuana cigarettes tend to be smoked without filters and are inhaled more deeply. This leads to higher amounts of smoke going deeper into the lungs than with cigarette smoking. Marijuana smoke leads to 5 times greater absorption of carbon monoxide than cigarettes. Due to how long marijuana smoke is held in the lungs, there is 4x more tar deposited in the lungs. Benzopyrene, a cancer-causing agent, is in marijuana and cigarettes.

Smoking marijuana can:

• Damage the lungs leading to asthma and chronic obstructive lung disease (COPD).
• Increase risk of getting mouth, tongue, and lung cancers.
• Decrease reproductive function (the ability to have a baby).
• Weaken the body’s immune system (the ability to fight infection).
• Increase risk of leukemia and other cancers in children whose mothers smoke marijuana during pregnancy.

Despite all that we know about the dangers of marijuana smoke, most of the studies have not found a strong link to cancer. This is more likely due to the small size of the studies and the difficulties mentioned above when studying marijuana use. Marijuana legalization in many areas may offer better quality studies going forward. Researchers agree that there is most likely some cancer-causing effect to smoking marijuana, but they have not been able to capture this in numbers with clinical studies yet.