Lung cancer is the most common cancer that is responsible for 21.1% of all cancer deaths among Israeli men, and 11.8% among women due to active and passive smoking.
As far as tobacco smoking is concerned, the data clearly demonstrate that smoking cigarettes and tobacco is destructive to the lungs and is directly related to an increase in lung cancer cases.
But what about marijuana and cannabis? There is an objective difficulty in conducting a comparative study between marijuana smokers and tobacco smokers because marijuana is illegal, and the results of the studies are contradictory.
When marijuana is smoked, THC is absorbed into the bloodstream through the lungs. Marijuana smoke contains a complex mixture of chemicals that bears a significant resemblance to tobacco smoke in both size and distribution in the air.
The widespread and increasing use of marijuana has raised concerns that it may cause short- and long-term respiratory complications including bronchitis, chronic lung disease and lung cancer.
A comprehensive research review by Dr. Manish and Anita Joshi and Dr. Thaddeus Barter revealed conflicting data.
Harms of smoking marijuana and cannabis to the lungs
Early research suggested that marijuana causes a decrease in lung capacity, although the data regarding the relationship between lung cancer and marijuana is not optimal. Meta-analyses with larger numbers of subjects reached the opposite conclusion.
The results of a comparative study by Aldington and his colleagues indicate that people who use both cannabis and tobacco have a response pattern similar to those who use only tobacco, but it will be more attenuated. Tan and colleagues reported that concurrent use of marijuana and tobacco was associated with an increased risk compared to tobacco use alone for obstructive pulmonary disease when more than 50 marijuana cigarettes were smoked. The conclusion of the studies is that tobacco is the dominant cause of damage to the health of those who use both products, and it is not clear what the contribution of marijuana is.
Maertens and colleagues used mouse lung epithelial cells to compare and contrast marijuana smoke (MSC) and tobacco smoke. The data clearly demonstrate a similar effect to cigarette smoke and marijuana smoke, and this study strengthens the link supporting the biological plausibility of marijuana smoking as a risk factor for the development of lung cancer. A 40-year follow-up study found a 2-fold risk of lung cancer in 831 subjects who reported heavy cannabis use more than 50 times they smoked.
The side effects of smoking marijuana – The side effects of smoking marijuana alone or in combination with tobacco were examined in 11 observational studies. Along with bronchial dilation, wheezing, increased coughing and sputum production were also found. It is likely that respiratory symptoms in marijuana smokers are due to changes in the lining of the large airways. The researchers concluded that smoking marijuana alone caused changes in the nucleus of lung cells, which may be pre-malignant. The collective data suggest that chronic marijuana smoking is often associated with major airway inflammation, which can be symptomatic.
Marijuana does not harm health
Studies over the years have found that after smoking marijuana, there was an immediate increase in the specific airways that peaked 15 minutes after smoking and remained elevated for about an hour, whether it was smoking or swallowing. After ingestion of 10 mg, airway conductance was significantly increased compared to placebo. Bronchodilation reached peak levels three hours later regardless of whether the marijuana was ingested or smoked, and airway conductance remained elevated for four to six hours.
Tashkin and colleagues subsequently reported a similar bronchodilator effect of cannabis also in patients with mild asthma. Marijuana can cause bronchitis and may affect lung health, but even when smoked, it does not cause chronic lung disease. A current summary of collective data claims that marijuana is not the cause of lung cancer.
These collective data suggest that marijuana may have some effect on lung function, but even if it does, it is still significantly different from those caused by tobacco.
Given the previous data, it is surprising that the collective clinical data does not prove a link between marijuana and lung cancer. The current epidemiological evidence regarding marijuana smoking and lung cancer contradicts a causal relationship. A recent study examined 611 types of lung cancer and found no link between marijuana use and lung cancer. Ghasemiesfe and his colleagues concluded that there is no evidence of any link between marijuana use and lung cancer.
In conclusion, one would expect marijuana to be associated with an increased risk of lung cancer. Older studies have confirmed this impression, but more recent studies have denied it. Today, researchers suggest that marijuana smoke may contain both harmful and beneficial substances. However, none of these conclusions are final because the difficulty of creating a sterile study is great, due to concurrent tobacco users, small sample size, young age of the participants, and underreporting. Marijuana has been shown to be much less toxic than tobacco, but it is reasonable to suggest caution against regular heavy marijuana use.
Marijuana has been used all over the world for thousands of years and its negative image has negatively affected the ability to use and study its ingredients. The prevalence of endocannabinoid receptors in marijuana has led to a better mechanistic understanding of marijuana’s ability to influence. Various components are known to help or may help in the treatment of epilepsy, nausea, anorexia, chronic pain, depression, and possibly cancer.
However, any use of marijuana must be examined based on the situations in which it can be harmful. Marijuana poses a danger to the developing brain, with an increased risk of addiction and possibly cognitive impairment and is therefore not recommended for youth. The studies on marijuana are contradictory but the principles are similar. Marijuana smoke contains harmful substances and protective substances. It can cause major inflammation in the airways, but it also dilates the bronchi and does not seem to cause minor damage to the airways.
Marijuana does not cause obstructive pulmonary disease. The collective literature suggests that marijuana does not cause lung cancer. The data supports further evaluation of the potential benefits of marijuana and its components and of alternative means of acquisition that bypass respiratory tract inflammation. The data on marijuana is in stark contrast to that of tobacco, the world’s biggest legal killer. Any potential toxicity of marijuana pales in comparison.
As pulmonologists we meet a lot of non-medical cannabis smokers and questions often arise in these meetings about the health consequences of this smoking. For example, incidental findings in chest imaging such as a chest x-ray or computed tomography in a cannabis smoker can be a benign finding, but it may be cancer.
Currently, there are various international criteria and guidelines that assist in making medical decisions regarding imaging findings with consideration of the individual’s years of smoking, but there is no specific reference to cannabis smokers. Often, in order to find out whether a finding in chest imaging is malignant or not, lung doctors perform a sample or biopsy using different methods.
Thanks to technological development, it is now possible to sample even the smallest lesions without the need for surgery or cutting the lung. Minimally invasive methods such as endobronchial navigation systems allow a pulmonologist to reach lesions that are a few millimeters in diameter with extremely delicate tools, to take a sample from them in a safe manner and even to destroy these lesions if necessary.
The author is a specialist in internal medicine and lung diseases, director of the invasive pulmonology service and secretary of the Israeli Pulmonary Medicine Association at the Ichilov Hospital