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Marijuana and cancer

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The Abramson Cancer Center of the University of Pennsylvania
Last Modified: May 8, 2013

Question

I am wondering if any cases of lung cancer (or other cancer) can result from smoking marijuana?

Answer

Barbara Campling, MD, Medical Oncologist, responds:

Yes, there is evidence that marijuana smoking can cause cancer, in particular lung cancer. Smoke from burning marijuana contains many of the same carcinogens found in tobacco smoke, some in even higher concentrations. It has been difficult to sort out the contribution of marijuana to lung cancer, since many marijuana smokers also use tobacco. Furthermore, it may be difficult to obtain accurate information about the use of illicit drugs. Here are a number of studies that you may want to look up:

1. Barsky SH, et al. Histopathologic and molecular alterations in bronchial epithelium in habitual smokers of marijuana, cocaine, and/or tobacco. Journal of the National Cancer Institute 90: 1198-1205 (1998). This group found premalignant changes in the airways of smokers of marijuana or crack cocaine that were very similar to the changes found in tobacco smokers. These changes were not detected in the airways of non-smokers.
2. Mao L, et al. Does marijuana or crack cocaine cause cancer? Journal of the National Cancer Institute 90: 1182-1184 (1998). This paper reviews the evidence for an association between marijuana use and lung cancer, as well as head and neck cancer.
3. Fung M, et al. Lung and aero-digestive cancers in young marijuana smokers. Tumori 85: 140-142 (1999). This is a report from the Department of Radiation Oncology at the University of Pennsylvania of a number of young patients with lung or other aero-digestive cancers who were marijuana users.