Q: Does smoking marijuana cause lung cancer the way smoking cigarettes does?

It’s still unclear whether smoking pot increases the risk for developing lung cancer. Hard data on the risks of marijuana smoking have been hard to come by because, until recently, cannabis was an illegal drug throughout the United States and so little scientific research was done. Marijuana contains tar and many of the same cancer-causing chemicals found in tobacco smoke. Marijuana joints are typically smoked all the way to the end, where the tar content is highest, and typically users inhale marijuana smoke very deeply and hold the smoke in their lungs for a long time. As a result, marijuana smoke leaves four times as much tar in the lungs as cigarette smoke. On the other hand, marijuana smokers tend to smoke less per day than cigarette smokers. Many marijuana users also smoke cigarettes, further clouding the data.

Studies looking at lung cancer rates among long-term marijuana smokers haven’t found any increased risk. And animal studies have suggested that compounds in marijuana may have antitumor effects. But further research is needed to accurately answer the question.