Cannabis-associated respiratory disease
Encyclopedia
Cannabis-associated respiratory disease can refer to neoplastic processes or to structural damage to the lung
.
It is often compared to the damage done by tobacco
, but it is the subject of much less study. Cannabis
is sometimes considered more dangerous because filters are usually not used, and sometimes considered less dangerous because different molecules are involved.
The process most popularly used to ingest cannabis is smoking, and for this reason most research has evaluated health effects from this method of ingestion. Other methods of ingestion may have lower or higher health risks. Tobacco smoking has well-established risks such as bronchitis
, cough
ing, overproduction of mucus
, wheezing, and addiction
. Similar risks for smoking cannabis related to airway inflammation
have been suggested in a study of healthy cannabis users who exhibited similar early characteristics to tobacco smoking
.
The effects of tobacco and cannabis smoking differ, however, as they affect different parts of the respiratory tract
: whereas tobacco tends to penetrate to the smaller, peripheral passageways of the lungs, cannabis tends to concentrate on the larger, central passageways. One consequence of this is that cannabis, unlike tobacco, does not appear to cause emphysema
, though this claim is disputed. A 2002 report by the British Lung Foundation
estimated that three to four cannabis cigarettes a day were associated with the same amount of damage to the lungs as 20 or more tobacco cigarettes a day. Unlike tobacco, regular cannabis use does not appear to cause chronic obstructive pulmonary disease
.
In some cases, cannabis users mix commercial tobacco in joints
, called "Spliff" (popular in Europe), tobacco mixed with hash in a chillum (India), or cannabis rolled in tobacco leaves (a blunt
), which would expose the user to the additional risks of tobacco, such as rapid physical addiction to nicotine
.
s. Surprisingly, an extensive study published in 2006 by Donald Tashkin of the University of California, Los Angeles
found that there is no significant link between smoking cannabis and lung cancer. The study, which involved a large population sample (1,200 people with lung, neck, or head cancer, and a matching group of 1,040 without cancer) found no correlation between marijuana smoking and increased lung cancer
risk, with the same being true for head and neck cancers as well. The results indicated no correlation between long and short-term cannabis use and cancer, indicating a possible therapeutic effect. Extensive cellular studies and some studies in animal models suggest that THC or cannabidiol
has antitumor properties, either by encouraging programmed cell death
of genetically damaged cells that can become cancerous, or by restricting the development of the blood supply that feeds tumors, or both. Unlike most other studies, this one had a very large sample size and was controlled for tobacco, alcohol, and several socio-demographic factors, which likely confounded the other studies.
In 2007 a significantly smaller study was released by the Medical Research Institute of New Zealand suggested that smoking cannabis increased the risk of lung cancer by 5.7 times over non-smokers. The small 79 person study noted that "In the near future we may see an 'epidemic' of lung cancers connected with this new carcinogen. And the future risk probably applies to many other countries, where increasing use of cannabis among young adults and adolescents is becoming a major public health problem."
Prior, a 1997 study examining the records of 64,855 Kaiser patients (14,033 of whom identified themselves as current smokers), also found no positive correlation between cannabis use and cancer.
Conversely, the 2008 case-control study from New Zealand mentioned earlier by the Cannabis and Respiratory Disease Research Group examining adults under age 55 with lung cancer concluded that smoking cannabis was significantly associated with risk of developing lung cancer, after controlling for smoking tobacco; the highest tertile
of marijuana smokers were estimated to have a 5.7-fold higher risk of lung cancer compared to nonusers.
A Research Triangle Institute study concluded that THC, a dilative agent (bronchodilator
), may help cleanse the lungs by dilating the bronchi, and could actively reduce the instance of tumors. Additionally, a study by Rosenblatt et al. found no association between marijuana use and the development of head and neck squamous cell carcinoma
. However, a contrasting study conducted in 2000 linked the smoking of cannabis to the growth of cancerous tumors through the impairment of anti-tumor defenses in mice.
A preliminary 2009 study found that cannabis use may increase the risk of testicular cancer
. In particular, the risk of developing nonseminoma testicular cancer, a more aggressive form of the disease, was increased in current cannabis users and even greater in long-term chronic users. This however is overshadowed by the fact that researchers are unable to determine what about marijuana causes the increased risk, or for that matter if a positive correlation can be established. A statement was released by the researchers that performed the study as seen below:
"This is the first study to look at this question, and by itself is not definitive. And there's a lot more research that would have to be done in order to prove that marijuana use really increases a man's risk of developing testicular cancer", - Stephen Schwartz.
Cannabis smoke (but not the plant itself) has recently been added to a "list of substances California regulators say cause cancer". California's Office of Environmental Health Hazard assessment has added cannabis smoke to the list after it found that it "contains 33 of the same harmful chemicals as tobacco smoke."
In a study of ten smokers with mild respiratory issues Hii et al. found evidence of lung disease in the form of severe bullae (fluid-filled, thin-walled blisters) of different shapes and sizes. Despite such lung disease, the patients' chest x-rays were normal and lung function was only mildly reduced in nearly half of the patients. The cannabis-smoking patient group was, on average, 41 years old—considerably younger than previously research tobacco-smoking patients with lung disease, who had an average age of between 62–67 years. The researchers conclude that the younger age of lung disease and poorer lung function may be due to different smoking patterns demonstrated in cannabis smokers, who have been found to inhale larger amounts of smoke, which is held in the lungs for longer periods of time.
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...
.
It is often compared to the damage done by tobacco
Tobacco
Tobacco is an agricultural product processed from the leaves of plants in the genus Nicotiana. It can be consumed, used as a pesticide and, in the form of nicotine tartrate, used in some medicines...
, but it is the subject of much less study. Cannabis
Cannabis
Cannabis is a genus of flowering plants that includes three putative species, Cannabis sativa, Cannabis indica, and Cannabis ruderalis. These three taxa are indigenous to Central Asia, and South Asia. Cannabis has long been used for fibre , for seed and seed oils, for medicinal purposes, and as a...
is sometimes considered more dangerous because filters are usually not used, and sometimes considered less dangerous because different molecules are involved.
The process most popularly used to ingest cannabis is smoking, and for this reason most research has evaluated health effects from this method of ingestion. Other methods of ingestion may have lower or higher health risks. Tobacco smoking has well-established risks such as bronchitis
Bronchitis
Acute bronchitis is an inflammation of the large bronchi in the lungs that is usually caused by viruses or bacteria and may last several days or weeks. Characteristic symptoms include cough, sputum production, and shortness of breath and wheezing related to the obstruction of the inflamed airways...
, cough
Cough
A cough is a sudden and often repetitively occurring reflex which helps to clear the large breathing passages from secretions, irritants, foreign particles and microbes...
ing, overproduction of mucus
Mucus
In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...
, wheezing, and addiction
Substance dependence
The section about substance dependence in the Diagnostic and Statistical Manual of Mental Disorders does not use the word addiction at all. It explains:...
. Similar risks for smoking cannabis related to airway inflammation
Inflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
have been suggested in a study of healthy cannabis users who exhibited similar early characteristics to tobacco smoking
Tobacco smoking
Tobacco smoking is the practice where tobacco is burned and the resulting smoke is inhaled. The practice may have begun as early as 5000–3000 BCE. Tobacco was introduced to Eurasia in the late 16th century where it followed common trade routes...
.
The effects of tobacco and cannabis smoking differ, however, as they affect different parts of the respiratory tract
Respiratory tract
In humans the respiratory tract is the part of the anatomy involved with the process of respiration.The respiratory tract is divided into 3 segments:*Upper respiratory tract: nose and nasal passages, paranasal sinuses, and throat or pharynx...
: whereas tobacco tends to penetrate to the smaller, peripheral passageways of the lungs, cannabis tends to concentrate on the larger, central passageways. One consequence of this is that cannabis, unlike tobacco, does not appear to cause emphysema
Emphysema
Emphysema is a long-term, progressive disease of the lungs that primarily causes shortness of breath. In people with emphysema, the tissues necessary to support the physical shape and function of the lungs are destroyed. It is included in a group of diseases called chronic obstructive pulmonary...
, though this claim is disputed. A 2002 report by the British Lung Foundation
British Lung Foundation
The British Lung Foundation is a British charity dedicated to promoting lung health and supporting those affected by lung disease.- About the British Lung Foundation :...
estimated that three to four cannabis cigarettes a day were associated with the same amount of damage to the lungs as 20 or more tobacco cigarettes a day. Unlike tobacco, regular cannabis use does not appear to cause chronic obstructive pulmonary disease
Chronic obstructive pulmonary disease
Chronic obstructive pulmonary disease , also known as chronic obstructive lung disease , chronic obstructive airway disease , chronic airflow limitation and chronic obstructive respiratory disease , is the co-occurrence of chronic bronchitis and emphysema, a pair of commonly co-existing diseases...
.
In some cases, cannabis users mix commercial tobacco in joints
Joint (cannabis)
Joint is a slang term for a cigarette rolled using cannabis. Rolling papers are the most common rolling medium among industrialized countries, however brown paper, cigarettes with the tobacco removed, and newspaper are commonly used in developing countries. Modern papers are now made from a wide...
, called "Spliff" (popular in Europe), tobacco mixed with hash in a chillum (India), or cannabis rolled in tobacco leaves (a blunt
Blunt (cigar)
A blunt is a cigar which is wider than a cigarillo and not quite as wide as a Corona. These cigars typically consist of two main parts; the inner leaf, which is similar to a cigarette rolling paper, except it is made of tobacco, and a thicker outer leaf which is rolled around the inner leaf in a...
), which would expose the user to the additional risks of tobacco, such as rapid physical addiction to nicotine
Nicotine
Nicotine is an alkaloid found in the nightshade family of plants that constitutes approximately 0.6–3.0% of the dry weight of tobacco, with biosynthesis taking place in the roots and accumulation occurring in the leaves...
.
Cancer risk
Cannabis smoke contains numerous carcinogenCarcinogen
A carcinogen is any substance, radionuclide, or radiation that is an agent directly involved in causing cancer. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes...
s. Surprisingly, an extensive study published in 2006 by Donald Tashkin of the University of California, Los Angeles
University of California, Los Angeles
The University of California, Los Angeles is a public research university located in the Westwood neighborhood of Los Angeles, California, USA. It was founded in 1919 as the "Southern Branch" of the University of California and is the second oldest of the ten campuses...
found that there is no significant link between smoking cannabis and lung cancer. The study, which involved a large population sample (1,200 people with lung, neck, or head cancer, and a matching group of 1,040 without cancer) found no correlation between marijuana smoking and increased lung cancer
Lung cancer
Lung cancer is a disease characterized by uncontrolled cell growth in tissues of the lung. If left untreated, this growth can spread beyond the lung in a process called metastasis into nearby tissue and, eventually, into other parts of the body. Most cancers that start in lung, known as primary...
risk, with the same being true for head and neck cancers as well. The results indicated no correlation between long and short-term cannabis use and cancer, indicating a possible therapeutic effect. Extensive cellular studies and some studies in animal models suggest that THC or cannabidiol
Cannabidiol
Cannabidiol is a cannabinoid found in Cannabis. It is a major constituent of the plant, representing up to 40% in its extracts.It has displayed sedative effects in animal tests...
has antitumor properties, either by encouraging programmed cell death
Programmed cell death
Programmed cell-death is death of a cell in any form, mediated by an intracellular program. PCD is carried out in a regulated process which generally confers advantage during an organism's life-cycle...
of genetically damaged cells that can become cancerous, or by restricting the development of the blood supply that feeds tumors, or both. Unlike most other studies, this one had a very large sample size and was controlled for tobacco, alcohol, and several socio-demographic factors, which likely confounded the other studies.
In 2007 a significantly smaller study was released by the Medical Research Institute of New Zealand suggested that smoking cannabis increased the risk of lung cancer by 5.7 times over non-smokers. The small 79 person study noted that "In the near future we may see an 'epidemic' of lung cancers connected with this new carcinogen. And the future risk probably applies to many other countries, where increasing use of cannabis among young adults and adolescents is becoming a major public health problem."
Prior, a 1997 study examining the records of 64,855 Kaiser patients (14,033 of whom identified themselves as current smokers), also found no positive correlation between cannabis use and cancer.
Conversely, the 2008 case-control study from New Zealand mentioned earlier by the Cannabis and Respiratory Disease Research Group examining adults under age 55 with lung cancer concluded that smoking cannabis was significantly associated with risk of developing lung cancer, after controlling for smoking tobacco; the highest tertile
Quantile
Quantiles are points taken at regular intervals from the cumulative distribution function of a random variable. Dividing ordered data into q essentially equal-sized data subsets is the motivation for q-quantiles; the quantiles are the data values marking the boundaries between consecutive subsets...
of marijuana smokers were estimated to have a 5.7-fold higher risk of lung cancer compared to nonusers.
A Research Triangle Institute study concluded that THC, a dilative agent (bronchodilator
Bronchodilator
A bronchodilator is a substance that dilates the bronchi and bronchioles, decreasing resistance in the respiratory airway and increasing airflow to the lungs. Bronchodilators may be endogenous , or they may be medications administered for the treatment of breathing difficulties...
), may help cleanse the lungs by dilating the bronchi, and could actively reduce the instance of tumors. Additionally, a study by Rosenblatt et al. found no association between marijuana use and the development of head and neck squamous cell carcinoma
Head and neck cancer
Head and neck cancer refers to a group of biologically similar cancers that start in the upper aerodigestive tract, including the lip, oral cavity , nasal cavity , paranasal sinuses, pharynx, and larynx. 90% of head and neck cancers are squamous cell carcinomas , originating from the mucosal lining...
. However, a contrasting study conducted in 2000 linked the smoking of cannabis to the growth of cancerous tumors through the impairment of anti-tumor defenses in mice.
A preliminary 2009 study found that cannabis use may increase the risk of testicular cancer
Testicular cancer
Testicular cancer is cancer that develops in the testicles, a part of the male reproductive system.In the United States, between 7,500 and 8,000 diagnoses of testicular cancer are made each year. In the UK, approximately 2,000 men are diagnosed each year. Over his lifetime, a man's risk of...
. In particular, the risk of developing nonseminoma testicular cancer, a more aggressive form of the disease, was increased in current cannabis users and even greater in long-term chronic users. This however is overshadowed by the fact that researchers are unable to determine what about marijuana causes the increased risk, or for that matter if a positive correlation can be established. A statement was released by the researchers that performed the study as seen below:
"This is the first study to look at this question, and by itself is not definitive. And there's a lot more research that would have to be done in order to prove that marijuana use really increases a man's risk of developing testicular cancer", - Stephen Schwartz.
Cannabis smoke (but not the plant itself) has recently been added to a "list of substances California regulators say cause cancer". California's Office of Environmental Health Hazard assessment has added cannabis smoke to the list after it found that it "contains 33 of the same harmful chemicals as tobacco smoke."
UCLA study
On 23 May 2006, Donald Tashkin, M.D., Professor of Medicine at the David Geffen School of Medicine at UCLA in Los Angeles announced that the use of cannabis does not appear to increase the risk of developing lung cancer, or increase the risk of head and neck cancers, such as cancer of the tongue, mouth, throat, or esophagus. The study involved 2252 participants, with some of the most chronic marijuana smokers having smoked over 22,000 marijuana cigarettes. The finding of Donald Tashkin, M.D., and his team of researchers in 2006 refined their earlier studies published in a Dec. 17th 2000 edition of the peer-reviewed journal Cancer Epidemiology Biomarker and Prevention. Many opponents of marijuana incorrectly cite the original finding of UCLA Medical Center from 2000 as "proof" that marijuana leaves the users at higher risk for cancer of the lung, and cancerous tumors, even though the researchers at the UCLA Medical Center have revised their finding with a more in-depth study on the effects of the use of marijuana. This seemed to contradict assumptions made after some studies, like those from Dale Gieringer et al., which found that 118 carcinogens were produced when marijuana underwent combustion, and two carcinogens {2-Methyl-2, 4(2H-1-benzopyran-5-ol) & 5-[Acetyl benz[e]azulene-3,8-dione} formed when marijuana underwent vaporization with the Volcano Vaporizer. To help explain this seemingly chemical proof of carcinogenicity inherent in the process of combustion, Tashkin noted that "one possible explanation for the new findings, he said, is that THC, a chemical in marijuana smoke, may encourage aging cells to die earlier and therefore be less likely to undergo cancerous transformation."In a study of ten smokers with mild respiratory issues Hii et al. found evidence of lung disease in the form of severe bullae (fluid-filled, thin-walled blisters) of different shapes and sizes. Despite such lung disease, the patients' chest x-rays were normal and lung function was only mildly reduced in nearly half of the patients. The cannabis-smoking patient group was, on average, 41 years old—considerably younger than previously research tobacco-smoking patients with lung disease, who had an average age of between 62–67 years. The researchers conclude that the younger age of lung disease and poorer lung function may be due to different smoking patterns demonstrated in cannabis smokers, who have been found to inhale larger amounts of smoke, which is held in the lungs for longer periods of time.