Exposure to Marijuana Smoke Does Not Effect Lungshttp://www.opposingviews.com/i/society/drug-law/jama-long-term-exposure-cannabis-smoke-not-associated-adverse-effects-pulmonary
NORML on Jan 10, 2012
Exposure to cannabis smoke, even over the long-term, is not associated with adverse effects on pulmonary function. That’s the conclusion of a major clinical trial published today in the prestigious Journal of the American Medical Association (JAMA).
Investigators at the University of California, San Francisco analyzed the association between marijuana exposure and pulmonary function over a 20 year period in a cohort of 5,115 men and women in four US cities.
Predictably, researchers “confirmed the expected reductions in FEV1 (forced expiratory volume in the first second of expiration) and FVC (forced vital capacity)” in tobacco smokers. By contrast, “Marijuana use was associated with higher FEV1 and FVC at the low levels of exposure typical for most marijuana users. With up to 7 joint-years of lifetime exposure (eg, 1 joint/d for 7 years or 1 joint/wk for 49 years), we found no evidence that increasing exposure to marijuana adversely affects pulmonary function.”
The study concludes, “Our findings suggest that occasional use of marijuana … may not be associated with adverse consequences on pulmonary function.”
To those familiar with the science of cannabis, JAMA’s findings should come as no great surprise. They are consistent with previous findings reporting no significant decrease in pulmonary function associated with moderate cannabis smoke exposure. For instance, according to a 2007 literature review conducted by researchers at the Yale University School of Medicine and published in the Archives of Internal Medicine, cannabis smoke exposure is not associated with airflow obstruction (emphysema), as measured by airway hyperreactivity, forced expiratory volume, or other measures.
Further, in 2006, the results of the largest case-controlled study ever to investigate the respiratory effects of marijuana smoking reported that cannabis use was not associated with lung-related cancers, even among subjects who reported smoking more than 22,000 joints over their lifetime. (Read NORML’s summary in the following article.)
“We hypothesized that there would be a positive association between marijuana use and lung cancer, and that the association would be more positive with heavier use,” the study’s lead researcher, Dr. Donald Tashkin of the University of California at Los Angeles stated. “What we found instead was no association at all, and even a suggestion of some protective effect” among marijuana smokers who had lower incidences of cancer compared to non-users.
A previous 1997 retrospective cohort study consisting of 64,855 examinees in the Kaiser Permanente multiphasic health checkup in San Francisco and Oakland also reported, “[E]ver- and current use of marijuana were not associated with increased risk of cancer … of the following sites: colorectal, lung, melanoma, prostate, breast, cervix.”
Separate studies of cannabis smoke and pulmonary function have indicated that chronic exposure may be associated with an increased risk of certain respiratory complications, including cough, bronchitis, phlegm. However, the ingestion of cannabis via alternative methods such as edibles, liquid tinctures, or via vaporization — a process whereby the plant’s cannabinoids are heated to the point of vaporization but below the point of combustion –- virtually eliminates consumers’ exposure to such unwanted risk factors and has been determined to be a ‘safe and effective’ method of ingestion in clinical trial settings.
Cannabis Smoking Not Linked To Lung Cancer, Case-Control Study Says
San Diego, CA: Smoking cannabis, even long-term, is not positively associated with increased incidence of lung-cancer, according to the findings of the largest population-based case-control study performed to date. Lead investigator Donald Tashkin of the David Geffen School of Medicine, Division of Pulmonary and Critical Care Medicine, at the University of California-Los Angeles, presented the results this week at the 2006 International Conference of the American Thoracic Society in San Diego.
Investigators assessed the possible association between cannabis use and the risk of lung cancer in middle-aged adults (ages 18-59) living in Los Angeles. Researchers conducted interviews with 611 subjects with lung cancer and 1,040 controls matched for age, gender and neighborhood. Data was collected on lifetime marijuana use, as well as subjects' use of alcohol, tobacco and other drugs, diet, occupation, and family history of cancer. Investigators used a logistical regression model to estimate the effect of cannabis smoking on lung cancer risk, adjusting for age, gender, ethnicity, education, and cumulative tobacco smoking and alcohol use.
"We did not observe a positive association of marijuana use -- even heavy long-term use -- with lung cancer, controlling for tobacco smoking and other potential cofounders," investigators concluded. Their data further revealed that one subset of moderate lifetime users (10-<30 "joint years") actually had an inverse association between cannabis use and lung cancer. The study did report a 20-fold increased risk in heavy tobacco smokers.Investigators also did not report a positive association between cannabis use and increased incidence of upper aerodigestive tract (UAT) cancers. The five-year trial was sponsored by the US National Institutes of Health (NIH).NORML Senior Policy Analyst Paul Armentano said that Tashkin's findings reaffirm the results of prior case-control studies dismissing a causal link between cannabis use and certain types of lung and upper aerodigestive tract (UAT) cancers. These include: a 2001 John Hopkins University hospital-based case-control study that found neither "lifetime use" nor "ever use" of cannabis were associated with head, neck or lung cancer in younger adults; a 2004 University of Washington case-control study that found "no association" between cannabis use and incidents of oral cancer, regardless of how long, how much or how often individuals had used it; and a 1997 Kaiser Permanente retrospective cohort study that found that cannabis use was not associated with increased risks of developing tobacco-use related cancers of the lung and upper aerodigestive tract or other cancers in men and women who used marijuana but did not smoke tobacco."The most remarkable aspect of this study is that its findings are, in fact, unremarkable," Armentano said. "As has been previously reported by the US Institute of Medicine and others, there is no conclusive evidence that marijuana causes cancer in humans, including those cancers generally related to tobacco use."Armentano suggested that cannabis consumers who desire the rapid onset of action associated with inhalation but who are concerned about the potential harms of noxious smoke can dramatically cut down on their intake of carcinogenic compounds by engaging in vaporization rather than smoking.For more information, please contact Paul Armentano, NORML Senior Policy Analyst, at (202) 483-5500. Additional information on cannabis and cancer is available in NORML's report, "Cannabis Smoke and Cancer: Assessing the Risk," available online at:
http://www.norml.org/index.cfm?Group_ID=6891
http://norml.org/news/2006/05/24/cannabis-smoking-not-linked-to-lung-cancer-case-control-study-says