Cannabis smoking does not cause cancer
According to a case-control study by Dr. Donald Tashkin and his colleagues of the University of California in Los Angeles even heavy and longterm smoking of cannabis is not associated with lung cancer and other types of upper aerodigestive tract cancers. The results were presented on 26 June at the annual conference of the International Cannabinoid Research Society (ICRS).
The study included 1,209 residents of Los Angeles aged 18-59 with cancer (611 lung, 403 oral/pharyngeal, 90 laryngeal, and 108 esophageal). Interviewers collected lifetime histories of cannabis, tobacco, alcohol and other drug use, and data on other factors that may influence cancer risk, including diet, occupational exposures, and family history of cancer. Exposure to cannabis was measured in joint years (1 joint year = 365 joints). The cancer patients were compared to 1,040 cancer- free controls. Among the controls 46 per cent had never used cannabis, 31 per cent had used it for less than one joint year, 12 per cent for 10-30 joint years, 2 per cent for 30-60 joint years, and 3 per cent for more than 60 joint years.
Compared with subjects who had used less than one joint year, the risk for lung cancer was 0.78 for 1-10 joint years, 0.74 for 10-30 joint years, 0.85 for 30-60 joint years, and 0.81 for more than 60 joint years. A risk below 1.0 means that the risk for cannabis users was slightly lower than for non-users. Similar results were obtained for the other cancer sites. There was no dose-response relationship of cancer risk, which means that there was no increased risks for more intensive users. The data on tobacco use, as expected, revealed a very potent effect and a clear dose-response relationship.
(Morgenstern H, et al. Marijuana use and cancers of the lung and upper aerodigestive tract: results of a case-control study. Presentation at the ICRS Conference on Cannabinoids, 24-27 June, Clearwater, USA)
