Washington, DC: The results of a recent study from New Zealand reporting a nearly six-fold increased risk of lung cancer for individuals who smoke cannabis are based on only 14 cases, and have never been replicated in large-scale population case-control studies, NORML Deputy Director Paul Armentano said today.
The widely reported study, published Friday in the European Respiratory Journal, assessed the relative risk of lung cancer associated with marijuana smoking in 79 cases and 324 controls. Of the 79 cases in the study, 70 reported smoking tobacco and 21 smoked cannabis.
Investigators reported that light-to-moderate lifetime cannabis use "was not associated with a significantly increased risk [of lung cancer]." By contrast, researchers reported that the 14 subjects in the study with the highest exposure to cannabis (more than one joint per day for 10 years) had a 5.7 times higher relative risk of lung cancer compared to controls. Overall, subjects who reported having ever smoked tobacco experienced a nearly seven-fold increase in lung cancer risk. By contrast, subjects who reported having ever used cannabis did not experience a statistically significant increased risk of lung cancer compared to non-using controls.
Previous large-scale population case control studies have also failed to identify a significant cancer risk associated with cannabis consumption. Most recently, a UCLA study of more than 2,200 subjects (1,212 cases and 1,040 controls) reported that marijuana smoking was not positively associated with cancers of the lung or upper aerodigestive tract – even among individuals who reported smoking more than 22,000 joints during their lifetime.
A prior Johns Hopkins University study of 164 oral cancer patients and 526 controls also concluded, "The balance of the evidence … does not favor the idea that marijuana as commonly used in the community is a causal factor for head, neck or lung cancer in adults [under age 55.]"
Finally, A 1997 Kaiser Permanente retrospective cohort study examining the relationship of marijuana use and cancer incidence in 65,171 men and women in California found that cannabis use was not associated with increased risks of developing tobacco-use related cancers – including lung cancer, breast cancer, prostate cancer, colorectal cancer, or melanoma.
"The release of this study does little to contradict the large body of existing science indicating that the moderate use of cannabis presents little-to-no known cancer risk," NORML Deputy Director Paul Armentano said. "By contrast, a growing body of evidence indicates that compounds in marijuana may, in fact, be protective against certain types of cancer, including lung cancer.
"Moreover, cannabis consumers concerned about the potential health risks posed by smoking may engage in vaporization to significantly reduce their intake of respiratory irritants or gaseous combustion toxins. For select marijuana consumers, such as patients using medicinal cannabis to treat a chronic condition, this method of ingestion is both preferable and advisable."
For more information, please contact Paul Armentano, NORML Deputy Director, at: firstname.lastname@example.org. Additional information on marijuana smoking and cancer risk is available in the online report, "Cannabis Smoke and Cancer: Assessing the Risk,’ at: http://www.norml.org/index.cfm?Group_ID=6891.