Study: Cannabis Smoking Not Associated With Increased Lung Cancer Risk Or Other Serious Pulmonary ComplicationsJune 19, 2013
A forthcoming review to be published in journal Annals of the American Thoracic Society reiterates that the ingestion of cannabis smoke poses nominal pulmonary risks compared to those associated with tobacco smoke. The author of the paper, Donald P. Tashkin, MD, emeritus professor of medicine and medical director of the Pulmonary Function Laboratory at the David Geffen School of Medicine at University of California, Los Angeles performed US-government sponsored studies of marijuana and lung function for over 30 years.
A preview of Dr. Tashkin’s forthcoming review appears on the American Thoracic Society news website here. It reads:
Dr. Tashkin found that regular smoking of marijuana by itself causes visible and microscopic injury to the large airways that is consistently associated with an increased likelihood of symptoms of chronic bronchitis that subside after cessation of use. He also found that the evidence does not indicate that habitual use of marijuana leads 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.
The author finds no clear link between marijuana use and the development of COPD or lower respiratory tract infections. In addition, “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,” Dr. Tashkin notes. “In summary, the accumulated weight of evidence implies far lower risks for pulmonary complications of even regular heavy use of marijuana compared to the grave pulmonary consequences of tobacco.”
The full paper will be available later this month.
In May, presenters at the annual meeting of the American Academy for Cancer Research reported that subjects who regularly inhale cannabis smoke possess no greater risk of lung cancer than do those who consume it occasionally or not at all — according to an analysis of six case-control studies, conducted between 1999 and 2012, involving over 5,000 subjects (2,159 cases and 2,985 controls) from around the world.
Last year, clinical data published in the Journal of the American Medical Association (JAMA) reported that subjects’ exposure to moderate levels of cannabis smoke, even over the long-term, is not associated with significant adverse effects on pulmonary function.
Vaporizers, which heat marijuana to a point where cannabinoid vapors form, but below the point of combustion, reduce subjects’ intake of potentially hazardous combustible compounds. In several clinical trials, investigators have concluded that vaporization is a “safe and effective” cannabinoid delivery mode that “does not result in exposure to combustion gases.” Researchers also report that vaporization results in higher plasma concentrations of THC compared to smoked cannabis.
Another study has once again affirmed that the enactment of statewide medical cannabis laws is not associated with increased rates of adolescent marijuana consumption.
According to data published this week in the American Journal of Public Health, the passage of medical marijuana laws in various states has had no “statistically significant … effect on the prevalence of either lifetime or 30-day marijuana use” by adolescents residing in those states.
Researchers at the University of Florida College of Medicine evaluated the effects of medical marijuana laws on adolescent marijuana use rates during the years 2003 and 2011. Investigators “found no evidence of intermediate-term effects of passage of state MMLs (medical marijuana laws) on the prevalence or frequency of adolescent nonmedical marijuana use in the states evaluated.” Authors concluded, “Our results suggest that, in the states assessed here, MMLs have not measurably affected adolescent marijuana use.”
The study’s findings rebut often repeated claims from cannabis prohibitionists that the passage of therapeutic cannabis laws adversely impacts teens’ usage of the substance.
In fact, numerous published studies have contradicted this claim. A 2012 analysis of statewide cannabis laws and adolescent use patterns of commissioned by the Institute for the Study of Labor (IZA) in Germany concluded: “Our results suggest that the legalization of medical marijuana was not accompanied by increases in the use of marijuana or other substances such as alcohol and cocaine among high school students. Interestingly, several of our estimates suggest that marijuana use actually declined with the passage of medical marijuana laws.”
A separate 2012 study by researchers at McGill University in Montreal and published in the journal Annals of Epidemiology reported similar findings, concluding: “[P]assing MMLs (medical marijuana laws) decreased past-month use among adolescents … and had no discernible effect on the perceived riskiness of monthly use. … [These] estimates suggest that reported adolescent marijuana use may actually decrease following the passing of medical marijuana laws.”
Previous investigations by research teams at Brown University in 2011 and Texas A&M in 2007 made similar determinations, concluding, “[C]onsistent with other studies of the liberalization of cannabis laws, medical cannabis laws do not appear to increase use of the drug.”
Full text of the study, “Effects of State Medical Marijuana Laws on Adolescent Marijuana Use,” appears online in the American Journal of Public Health.
Preclinical study data published online in the scientific journal Nutrition & Diabetes reports that tetrahydrocannabivarin (THCV) — a naturally occurring analogue of THC — possesses positive metabolic effects in animal models of obesity.
British researchers assessed the effects of THCV administration on dietary-induced and genetically modified obese mice. Authors reported that although THCV administration did not significantly affect food intake or body weight gain in any of the models, it did produce several metabolically beneficial effects, including reduced glucose intolerance, improved glucose tolerance, improved liver triglyceride levels, and increased insulin sensitivity.
Researchers concluded: “Based on these data, it can be suggested that THCV may be useful for the treatment of the metabolic syndrome and/or type 2 diabetes (adult onset diabetes), either alone or in combination with existing treatments. Given the reported benefits of another non-THC cannabinoid, CBD in type 1 diabetes, a CBD/THCV combination may be beneficial for different types of diabetes mellitus.”
Last month, Harvard Medical School researchers published observational data in The American Journal of Medicine reporting that subjects who regularly consume cannabis possess favorable indices related to diabetic control as compared to occasional consumers or non-users of the substance. Writing in an accompanying commentary, the journal’s Editor-in-Chief stated: “These are indeed remarkable observations that are supported, as the authors note, by basic science experiments that came to similar conclusions. … I would like to call on the NIH and the DEA to collaborate in developing policies to implement solid scientific investigations that would lead to information assisting physicians in the proper use and prescription of THC in its synthetic or herbal form.”
Observational trial data published in 2012 in the British Medical Journal previously reported that adults with a history of marijuana use had a lower prevalence of type 2 diabetes and possess a lower risk of contracting the disease than did those with no history of cannabis consumption, even after researchers adjusted for social variables such as subjects’ ethnicity and levels of physical activity.
Full text of the study, “The cannabinoid ?9-tetrahydrocannabivarin (THCV) ameliorates insulin sensitivity in two mouse models of obesity,” is available online here.
Recent preclinical studies published over the past several weeks provide further evidence that cannabinoids are both neuroprotective and cardioprotective.
A May 30th blog post on the website Science20.com sums up new findings from Israel regarding the ability of low doses of THC to prevent brain damage in animals.
Prof. Yosef Sarne in the Department of Physiology and Pharmacology at Tel Aviv University says that [cannabis] … has neuroprotective qualities. He has found that extremely low doses of THC — the psychoactive component of marijuana — protects the brain from long-term cognitive damage in the wake of injury from hypoxia (lack of oxygen), seizures, or toxic drugs.
Previous studies focused on injecting high doses of THC within a very short time frame – approximately 30 minutes – before or after injury. Sarne’s papers in Behavioural Brain Research and Experimental Brain Research say that even extremely low doses of THC – around 1,000 to 10,000 times less than that in a conventional marijuana cigarette – administered over a wide window of 1 to 7 days before or 1 to 3 days after injury can jump-start biochemical processes which protect brain cells and preserve cognitive function over time.
… In the lab, the researchers injected mice with a single low dose of THC either before or after exposing them to brain trauma. A control group of mice sustained brain injury but did not receive the THC treatment. When the mice were examined 3 to 7 weeks after initial injury, recipients of the THC treatment performed better in behavioral tests measuring learning and memory. Additionally, biochemical studies showed heightened amounts of neuroprotective chemicals in the treatment group compared to the control group.
… This treatment, especially in light of the long time frame for administration and the low dosage, could be applicable to many cases of brain injury and be safer over time, Sarne says.
NORML has previously reported on separate preclinical data documenting that cannabinoids can promote neurogenesis (the active production of new neurons) in laboratory animals as well observational data indicating that marijuana may provide neuroprotection against alcohol-induced impairment in adolescent subjects.
In addition, recently published preclinical studies also indicate that cannabinoids may offer benefits to the heart. Animal data published in the June issue of the scientific journal Biochemical Pharmacology reports that THC administration “is a safe and effective treatment that reduces myocardial ischemic (heart attack) damage.” Authors concluded: “[O]ur study provides novel evidence for the beneficial use of extremely low doses of THC, doses that do not elicit any psychoactive side effects, in order to protect the heart from ischemic insults. THC can be used as a pre-conditioning drug in cases in which ischemic insult to the heart is anticipated, such as during cardiac surgery or percutaneous coronary intervention. If post-conditioning with THC will be found effective, it could also be used following myocardial infarction.”
The results of a separate preclinical trial, published in May in the journal Environmental Toxicology and Pharmacology, report that the administration of the non-psychotropic cannabinoid cannabidiol (CBD) is protective against cardiotoxicity in rats. “[C]annabidiol ameliorated doxorubicin-induced cardiac injury,” the study concluded. “These results indicate that cannabidiol represents a potential protective agent.”
In February of this year, investigators at the Bar-Ilan University in Israel also reported that the administration of delta-9-THC protects heart muscle cells from injury during hypoxia (a deficiency in the levels of oxygen in the blood). THC “delaying the onset of irreversible cell injury … on hypoxia-exposed cardiac cells in culture,” authors found. They concluded, “This research demonstrates that THC has beneficial effects on cardiac cells and supports the consideration of marijuana for specific medical uses.”
Last week, the Oregon House of Representatives voted 36 to 23 in favor of Senate Bill 281, which adds Post Traumatic Stress Disorder (PTSD) as a qualifying condition to the state’s medical marijuana program.
Speaking in favor of the bill, Rep. John Lively (D-Springfield) stated, “Each person who suffers has different levels of how they’re impacted and what it takes to recover. This is about providing a legal avenue for people suffering from PTSD.”
SB 281 was previously approved by the State Senate in April and now awaits Governor Kitzhaber’s signature.
You can read local media coverage here.