Washington, D.C.: Marijuana smokers appear to be at a significantly lower risk of developing cancer than tobacco smokers, according to an article by Amanda Chen et al. published in the Journal of Psychoactive Drugs (Sept, 2008).
The authors analyzed existing evidence on the carcinogenicity of marijuana smoke. Although it has long been hypothesized that marijuana smoke might cause cancer because it contains tars with known carcinogenic properties, like tobacco smoke, the authors note that epidemiological studies have so far failed to show a convincing causal relation between marijuana and smoking-related cancers.
The authors statistically re-analyzed previously published data on marijuana smoking and cancer, originally published by Dr. Stephen Sidney of Kaiser-Permante Medical Care in 1997. They looked at data on 64,833 subjects, including marijuana-only smokers, tobacco-only smokers, marijuana-and-tobacco smokers, and non-smokers, and analyzed their incidence of cancer, including lung, colorectal, prostate, breast, cervix, and tobacco-related cancers. In every case, they found a significantly lower risk of cancer for marijuana-only smokers than tobacco-only smokers.
There was not enough evidence to assess the cancer risk of marijuana smokers relative to non-smokers. While the authors noted there is some evidence to suggest that the cannabinoids in marijuana may actually suppress cancer, they concluded that more studies are needed to settle the question one way or another. In the meantime, says Dr. Sidney, the conclusions of his original study stand: “marijuana use and cancer were not associated” (“Marijuana use and cancer incidence (California, United States),” Cancer Causes and Control, Vol. 8, 1997).
For more information, please contact Dale Gieringer, California, NORML Director, or Paul Armentano, NORML Deputy Director. Full text of the study, by Amanda L.C. Chen et al., “Hypothesizing that Marijuana Smokers are at a Significantly Lower Risk of Carcinogenicity Relative to Tobacco-Non-Marijuana Smokers: Evidenced Based on Statistical Reevaluation of Current Literature,” appears in the Journal of Psychoactive Drugs, Sept 2008.Dale Gieringer – California NORML, (415) 563- 5858 – www.canorml.org.