Lung health and marijuana
THC has been found to reduce tumor growth in common lung cancer by 50 percent and to significantly reduce the ability of the cancer to spread, say researchers at Harvard University, who tested the chemical in both lab and mouse studies. The researchers suggest that THC might be used in a targeted fashion to treat lung cancer.
Although the researchers do not know why THC inhibits tumor growth, they say the substance could be activating molecules that arrest the cell cycle. They speculate that THC may also interfere with angiogenesis and vascularization, which promotes cancer growth.
In 2006, Donald Tashkin, M.D., of the University of California in Los Angeles found that unlike tobacco, smoking marijuana does not appear to increase the risk of lung cancer or head-and-neck malignancies, even among heavy users. The more tobacco a person smoked, the greater their risk of developing lung cancer and other cancers of the head and neck. But people who smoked more marijuana were not at increased risk compared with people who smoked less and people who didn’t smoke at all. Details of the study here.
The findings surprised the study’s researchers, who expected to see an increase in cancer among people who smoked marijuana regularly in their youth.
Marijuana use was associated with cancer risk ratios below 1.0, indicating that a history of pot smoking had no effect on the risk for respiratory cancers. In contrast, tobacco smoking had a 21-fold risk for cancer. Tashkin concluded that it’s possible that tetrahydrocannabinol (THC) in marijuana smoke may encourage apoptosis, or programmed cell death, causing cells to die off before they have a chance to undergo malignant transformation.
Similar findings on the safety of smoked marijuana were released in April 2009 by the Vancouver Burden of Obstructive Lung Disease Research Group. The study presents that smoking both tobacco and marijuana synergistically increased the risk of respiratory symptoms and COPD. Smoking only marijuana, however, was not associated with an increased risk of respiratory symptoms of COPD.
In a related commentary, Dr. Donald Tashkin writes that “the findings — add to the limited evidence of an association between marijuana use and COPD because [the] study focuses on an older population (aged 40 or older) that is at greater risk of COPD.” previous studies have failed to find an additive effect of marijuana and tobacco on either chronic respiratory symptoms or abnormal lung function in younger smokers. Dr. Tashkin states that “we can be close to concluding that marijuana smoking by itself does not lead to COPD.””.
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