ScienceDaily (Aug. 5, 2009) - In a finding that challenges the increasingly popular belief that smoking marijuana is less harmful to health than smoking tobacco, researchers in Canada are reporting that smoking marijuana, like smoking tobacco, has toxic effects on cells. Read more at website or click below:
Rebecca Maertens and colleagues note that people often view marijuana as a "natural" product and less harmful than tobacco. As public attitudes toward marijuana change and legal restrictions ease in some countries, use of marijuana is increasing.
Scientists know that marijuana smoke has adverse effects on the lungs. However, there is little knowledge about marijuana's potential to cause lung cancer due to the difficulty in identifying and studying people who have smoked only marijuana.
The new study begins to address that question by comparing marijuana smoke vs. tobacco smoke in terms of toxicity to cells and to DNA. Scientists exposed cultured animal cells and bacteria to condensed smoke samples from both marijuana and tobacco. There were distinct differences in the degree and type of toxicity elicited by marijuana and cigarette smoke.
Marijuana smoke caused significantly more damage to cells and DNA than tobacco smoke, the researchers note. However, tobacco smoke caused chromosome damage while marijuana did not.
Scientists know that marijuana smoke has adverse effects on the lungs. However, there is little knowledge about marijuana's potential to cause lung cancer due to the difficulty in identifying and studying people who have smoked only marijuana.
The new study begins to address that question by comparing marijuana smoke vs. tobacco smoke in terms of toxicity to cells and to DNA. Scientists exposed cultured animal cells and bacteria to condensed smoke samples from both marijuana and tobacco. There were distinct differences in the degree and type of toxicity elicited by marijuana and cigarette smoke.
Marijuana smoke caused significantly more damage to cells and DNA than tobacco smoke, the researchers note. However, tobacco smoke caused chromosome damage while marijuana did not.
Cannabis has been used by millions of Americans for decades. Its possible links to lung cancer and other lung diseases has been examined in thousands of subjects. Researchers are well aware of the lag time between smoking and the later development of lung cancer, this has been examined too.
ReplyDeleteAfter much study, cannabis smoke does not appear to be a significant cause of lung cancer or serious lung disease (minor issues like chronic cough and bronchitis can appear in heavier consumers). Besides, it does not need to be smoked, it can be cooked into foods or vaporized as well. Legalization makes these methods more accessible.
In 2013 the International Lung Cancer Consortium, an international group of lung cancer researchers, found no significant additional lung cancer risk in tobacco users who also smoked cannabis. Nor did they find an increased risk in cannabis smokers who did not use tobacco. They found that based on over 5,000 cases and controls, "Our pooled results showed no significant association between the intensity, duration, or cumulative consumption of cannabis smoke and the risk of lung cancer overall or in never smokers."
Zhang et al. Cannabis smoking and lung cancer risk: pooled analysis in the International Lung Cancer Consortium. Cancer Research. 2013.
Recent large scale studies have shown that serious adverse effects on the lung are unlikely, except possibly in the very heaviest of smokers (usually considered 5+ joints/day, data is lacking since so few use these amounts). A 2013 review of studies by one of the world's leading experts the effects of cannabis on the lung concluded that tobacco is FAR more harmful:
"On the other hand, habitual use of marijuana alone does not appear to lead to significant abnormalities in lung function when assessed either cross-sectionally or longitudinally, except for possible increases in lung volumes and modest increases in airway resistance of unclear clinical significance."
"findings from a limited number of well-designed epidemiological studies do not suggest an increased risk for the development of either lung or upper airway cancer from light or moderate use, although evidence is mixed concerning possible carcinogenic risks of heavy, long-term use."
"In summary, the accumulated weight of evidence implies far lower risks for pulmonary complications of even regular heavy use of marijuana compared with the grave pulmonary consequences of tobacco."
Tashkin DP. Effects of marijuana smoking on the lung. Ann Am Thorac Soc. 2013. Review.
A recent study published in The Journal of the American Medical Association also found little evidence of adverse pulmonary function:
"With up to 7 joint-years of lifetime exposure (e.g., 1 joint/day for 7 years or 1 joint/week for 49 years), we found no evidence that increasing exposure to marijuana adversely affects pulmonary function"
Pletcher et al. Association between marijuana exposure and pulmonary function over 20 years. JAMA. 2012.
Also, there are many peer-reviewed studies showing that the cannabinoids contained in cannabis, especially THC and CBD, directly fight tumors both by reducing their ability to spread and by shrinking them. Considering this, it is very plausible that increased cannabis use will not lead to significantly increased cancer incidence and may even reduce it. Regardless, even if smoking cannabis did increase the risk of lung cancer or lung disease, this would not be a valid reason to criminalize millions of Americans for using it.