The Health Effects of Cannabis and Cannabinoids The Current State of Evidence and Recommendations for Research (2017) / Chapter Skim
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7 Respiratory Disease
7 Respiratory Disease
Pages 181-198
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From page 181... ...
• It is unclear whether cannabis use is associated with chronic obstructive pulmonary disorder, asthma, or worsened lung function. Environmental exposures are the leading causes of respiratory disease worldwide.
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From page 182... ...
6) concluded that cannabis smoking was an important risk factor in the development of respiratory disease and recommended that "studies to define the individual health risks of smoking marijuana should be conducted, particularly among populations in which marijuana use is prevalent." The literature search conducted by the current committee did not identify any fair- or good-quality systematic reviews for cannabis use and respiratory disease published since 2011 (the cutoff established by the current committee)
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From page 183... ...
(2007) found a significantly lower FEV1/FVC, lower specific airways conductance, and a higher total lung capacity per joint-year smoked in cannabis smokers compared to nonsmokers.
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From page 184... ...
There was also an important decrease in exhaled nitric oxide among current smokers when compared to never smokers (−7 percent versus −14 percent) , but it is unclear if this effect was confounded by the high prevalence of tobacco smoking in current cannabis users or if it represented a true decrease in exhaled nitric oxide due to cannabis smoking.
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From page 185... ...
Many studies failed to control for tobacco smoking and occupational and other environmental exposures; did not control for the dose or duration of cannabis smoking; and did not use joint-years and instead based heavy cannabis smoking on having exceeded a specific threshold of joints. Even among studies that used joint-years, it is unclear how generalizable their findings are, given the potential high variability in lung-toxic content from joint to joint.
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From page 186... ...
. CHRONIC OBSTRUCTIVE PULMONARY DISEASE COPD is a clinical syndrome that consists of lower airway inflammation and damage that impairs airflow.
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From page 187... ...
There was inconsistent evidence for whether synergy from combined cannabis and tobacco smoking might affect the odds of having COPD or worse respiratory symptoms. Specifically, the mean estimates for the tobacco and cannabis smoking versus tobacco-only smoking groups do not appear to be different, and the 95% CI for the tobacco and cannabis smoking group appears to overlap significantly with the tobacco-only smoking groups when evaluating either COPD or respiratory symptoms as the outcome.
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From page 188... ...
Discussion of Findings It is unclear whether regular cannabis use is associated with the risk of developing COPD or exacerbating COPD. Current studies may be confounded by tobacco smoking and the use of other inhaled drugs as well as by occupational and environmental exposures, and these studies have failed to quantify the effect of daily or near daily cannabis smoking on COPD risk and exacerbation.
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From page 189... ...
RESPIRATORY SYMPTOMS, INCLUDING CHRONIC BRONCHITIS Respiratory symptoms include cough, phlegm, and wheeze. Chronic bronchitis is defined as chronic phlegm production or productive cough for 3 consecutive months per year for at least 2 consecutive years (Medical Research Council, 1965)
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From page 190... ...
, and chronic bronchitis symptoms (19 percent versus 3 percent) among cannabis smokers than among nonsmokers.
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From page 191... ...
They quantified frequency, amount, and degree of usual and maximal intoxication, and they also asked about respiratory symptoms using a composite score produced from the answers to six standard questions about cough, morning phlegm, dyspnea, chest wheezing other than during colds, and nighttime awakenings because of chest tightness. They found that the frequency of use, the amount used (in quarter bags per month)
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From page 192... ...
Cannabis smoking cessation was temporally associated with the resolution of chronic bronchitis symptoms, and a small feasibility study suggests that use of a vaporizer instead of smoking cannabis may lead to the resolution of respiratory symptoms. The committee's findings are consistent with those reported in a recent review (Tashkin, 2013)
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From page 193... ...
In this study, the investigators found that 16 percent of the adolescents smoked cannabis, but there was no association between cannabis use and asthma concern or asthma severity or asthma symptoms. The limitations of this study include the reliance on the self-report of cannabis use, which the study authors speculated may be underreported in black adolescents when compared to whites, and a lack of data on asthma medication adherence.
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From page 194... ...
Further research is needed to better elucidate the influence of exposure levels to cannabis smoke on respiratory outcomes, the chronicity of cannabis smoking, the effects of an underlying predisposition to respiratory disease, and possible interaction effects with tobacco smoke to promote airway inflammation, worsen respiratory symptoms, accelerate lung function decline, or increase exacerbation of COPD and asthma. Previous studies have not been able to adequately separate cannabis smoke effects from tobacco smoke effects, and this has meant that some important questions remain unanswered.
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From page 195... ...
Overall, the risks of respiratory complications of cannabis smoking appear to be relatively small and to be far lower than those of tobacco smoking. While heavy cannabis users may be at a higher risk for developing chronic bronchitis and COPD or at an increased risk of exacerbating COPD and asthma, current studies do not provide sufficient evidence for a link.
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From page 196... ...
There is limited evidence of a statistical association between cannabis smoking and: • increased risk of developing chronic obstructive pulmonary disease An (COPD) when controlled for tobacco use (occasional cannabis smoking)
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From page 197... ...
2016. Recent marijuana use and associations with exhaled nitric oxide and pulmonary function in adults in the United States.
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From page 198... ...
1987. Respiratory symptoms and lung function in habitual heavy smokers of marijuana alone, smokers of marijuana and tobacco, smokers of tobacco alone, and nonsmokers.
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