Respiratory status of seventy-four habitual marijuana smokers

Impact of Marijuana Use on Lung Health

The widespread use of marijuana in the context of increasing legalization has both short- and long-term health implications. Although various modes of marijuana use-smoked, vaped, or ingested-may lead to a wide scope of potential systemic effects, we focus here on inhalational use of marijuana as the most common mode with the lung as the organ that is most directly exposed to its effects. Smoked marijuana has been associated with symptoms of chronic bronchitis and histopathologic changes in airway epithelium, but without consistent evidence of long-term decline in pulmonary function. Its role in immunomodulation, both for risk of infection and protection against a hyperinflammatory host response to infection, has been suggested in animal models and in vitro without conclusive extrapolation to humans. Marijuana smoke contains carcinogens like those found in tobacco, raising concern about its role in lung cancer, but evidence is mixed and made challenging by concurrent tobacco use. Vaping may offer a potential degree of harm reduction when compared with smoking marijuana with reduction of exposure to several toxins, including carbon monoxide, and reduction in chronic respiratory symptoms. However, these potential benefits are counterbalanced by risks including vaping-associated lung injury, potentially more intense drug exposure, and other yet not well-understood toxicities. As more states legalize marijuana and the federal government considers changing this from a Schedule I to a Schedule III controlled substance, we anticipate an increase in prospective medical studies concerning the risks related to marijuana use. This review is based on currently available data concerning the impact of inhaled marijuana on lung health.

The Puzzle of Marijuana Use and Forced Vital Capacity

In study after study, marijuana use has been found to be associated with increased forced vital capacity (FVC). This is puzzling, because marijuana is commonly consumed by inhalation of its smoke, and smoke exposure of any kind is not generally considered a cause of increased FVC. Although this observation was first made decades ago, a satisfactory explanation remains elusive. In this review we survey the evidence supporting the relationship between marijuana use and increased FVC, discuss potential threats to validity when inferring causation, and, presupposing a possible causal relationship, pose two key questions. First, what are possible physiologic or pathophysiologic mechanisms by which marijuana use might increase FVC? Second, why might this effect be consistently observed with marijuana use but not with tobacco use? Explanations for the first question include lung and chest growth and remodeling from strenuous marijuana smoke inhalation and reductions in lung elastic recoil from marijuana smoke exposure. Explanations for the second include differences between marijuana and tobacco in smoke composition and patterns of consumption, such as smoking topography. Finally, the possibility that smoke, whether from marijuana or tobacco, might have nonmonotonic effects on FVC depending on the degree of exposure is explored. In synthesizing a curated breadth of epidemiologic and physiologic science, we leverage a perplexing observation to generate potential insights and avenues for further research into the biological effects of smoke, from marijuana or otherwise, on the respiratory system.

Cannabis and Cannabinoids in the Perioperative Period

Cannabis use is increasingly common, and with a growing number of jurisdictions implementing legalization frameworks, it is likely that providers will encounter more patients who use cannabis. Therefore, it is important for providers to understand the implications of cannabis use and practical considerations for the perioperative period. Cannabis affects multiple organ systems and may influence intraoperative anesthesia, as well as postoperative pain management. The effects of cannabis and key anesthetic considerations are reviewed here.

Effects of Smoking Marijuana on the Respiratory System: A Systematic Review

BACKGROUND

The prevalence of marijuana use and its derivatives has surged over the past century, largely due to increasing legalization globally. Despite arguments advocating its benefits, marijuana smoking exposes the lungs to harmful combustion byproducts, leading to various respiratory issues such as asthma, pneumonia, emphysema, and chronic obstructive pulmonary disease.

METHODS

We embarked on an extensive literature search, utilizing PubMed/Medline, Scopus, Web of Science, and Google Scholar databases, identifying 200 studies. After the elimination of duplicates, and meticulous review of abstracts and full texts, 55 studies were included in our analysis.

RESULTS

Current literature demonstrates that marijuana use negatively impacts lung function, triggering symptoms like chronic cough, sputum production, and wheezing, and diminishing FEV1/FVC ratio in spirometry tests. Moreover, prolonged or chronic marijuana use augments the risk of respiratory function impairment. While the carcinogenic effects of marijuana are still contested, a weak correlation between marijuana use and lung cancer has been observed in some studies. Additionally, instances of other pathologies linked to marijuana use have been reported, including the development of COPD, pulmonary bullae, spontaneous pneumothorax, pleuritic pain, chronic pulmonary aspergillosis, hemoptysis, and pulmonary Langerhans cell histiocytosis.

CONCLUSIONS

The evidence underscores that marijuana use is detrimental to respiratory health. In light of the escalating trend of marijuana use, particularly among the youth, it is imperative to advocate public health messages discouraging its consumption.

Marijuana and the Lung: Evolving Understandings

Human beings have used marijuana products for centuries. Relatively recent data showing extensive cannabinoid receptors, particularly in the brain, help to explain the impacts of cannabinoids on symptoms/diseases, such as pain and seizures, with major nervous system components. Marijuana can cause bronchitis, but a moderate body of literature suggests that distal airway/parenchymal lung disease does not occur; marijuana does not cause chronic obstructive pulmonary disease and probably does not cause lung cancer, distinctly different from tobacco. Potentials for cognitive impairment and for damage to the developing brain are contextually important as its beneficial uses are explored.

Inhaled Marijuana and the Lung

Although vaping has recently increased as a mode of inhaling marijuana and has been associated with numerous and sometimes fatal cases of acute severe lung injury, smoking remains the most common method of inhaling marijuana and has been studied more extensively. Smoking marijuana has been shown to produce modest but significant short-term bronchodilation both in healthy subjects and those with asthma. Long-term effects of habitual marijuana smoking include the following: 1) symptoms of chronic bronchitis (increased cough, sputum production and wheezing); 2) modest effects on lung function in cross-sectional studies (no significant decrease in forced expired volume in 1 second [FEV₁) but mild reductions in FEV₁/forced vital capacity ratio [FEV₁/FVC], an increase in FVC and other lung volumes, reductions in specific airway conductance, and variable effects of maximal mid-expiratory flow rates and diffusing capacity; and 3) variable effects on age-related decline in FEV1 in longitudinal studies. Most cohort and case-control studies have failed to show that marijuana smoking is a significant risk-factor for lung cancer despite the presence of pro-carcinogenic components in marijuana smoke, although further study is warranted. The question whether marijuana smoking is associated with asthma is unclear and requires further investigation. Although delta-9 tetrahydrocannabinol (THC), the principal psychoactive component of marijuana, has immunomodulatory properties that hypothetically could increase the risk of pneumonia, the few available studies in marijuana smokers have failed to find an increased risk of pneumonia in immunocompetent users, although effects in immunosuppressed individuals have been variable.

Differential Effects of Cannabis and Tobacco on Lung Function in Mid-Adult Life

Rationale: Evidence suggests that the effects of smoking cannabis on lung function are different from tobacco. However, long-term follow-up data are scarce and mostly based on young adults. Objectives: To assess the effects of cannabis and tobacco on lung function in mid-adult life. Methods: Cannabis and tobacco use were reported at ages 18, 21, 26, 32, 38, and 45 years in a population-based cohort study of 1,037 participants. Spirometry, plethysmography, and carbon monoxide transfer factor were measured at age 45. Associations between lung function and cannabis use were adjusted for tobacco use. Measurements and Main Results: Data were available from 881 (88%) of 997 surviving participants. Cumulative cannabis use was associated with lower FEV₁/FVC ratios, owing to a tendency toward higher FVCs. Cannabis use was also associated with higher TLC, FRC, residual volume, and Va along with lower midexpiratory flows, airway conductance, and transfer factor. Quitting regular cannabis use between assessments was not associated with changes in spirometry. Conclusions: Cannabis use is associated with higher lung volumes, suggesting hyperinflation. There is evidence of increased large-airway resistance and lower midexpiratory airflow, but impairment of FEV₁/FVC ratio is because of higher FVC. This pattern of effects is different to those of tobacco. We provide the first evidence that lifetime cannabis use may be associated with impairment of gas transfer.

Cannabis use disorder and the lungs

Cannabis is one of the world's most widely used recreational drugs and the second most commonly smoked substance. Research on cannabis and the lungs has been limited by its illegal status, the variability in strength and size of cannabis cigarettes (joints), and the fact that most cannabis users also smoke tobacco, making the effects difficult to separate. Despite these difficulties, the available evidence indicates that smoking cannabis causes bronchitis and is associated with changes in lung function. The pattern of effects is surprisingly different from that of tobacco. Whereas smoking cannabis appears to increase the risk of severe bronchitis at quite low exposure, there is no convincing evidence that this leads to chronic obstructive pulmonary disease. Instead, cannabis use is associated with increased central airway resistance, lung hyperinflation and higher vital capacity with little evidence of airflow obstruction or impairment of gas transfer. There are numerous reports of severe bullous lung disease and pneumothorax among heavy cannabis users, but convincing epidemiological data of an increased risk of emphysema or alveolar destruction are lacking. An association between cannabis and lung cancer remains unproven, with studies providing conflicting findings.

Associations of marijuana with markers of chronic lung disease in people living with HIV

OBJECTIVES

The relationship between marijuana use and markers of chronic lung disease in people living with HIV (PLWH) is poorly understood.

METHODS

We performed a cross-sectional analysis of the Examinations of HIV-Associated Lung Emphysema (EXHALE) study, including 162 HIV-positive patients and 138 participants without HIV. We modelled marijuana exposure as: (i) current daily or weekly marijuana smoking vs. monthly or less often; or (ii) cumulative marijuana smoking (joint-years). Linear and logistic regression estimated associations between marijuana exposure and markers of lung disease, adjusted for tobacco smoking and other factors.

RESULTS

In PLWH, current daily or weekly marijuana use was associated with a larger forced vital capacity (FVC), larger total lung capacity and increased odds of radiographic emphysema compared with marijuana non-smokers in adjusted models; these associations were not statistically significant in participants without HIV. Marijuana joint-years were associated with higher forced expiratory volume in 1 s and FVC in PLWH but not with emphysema.

CONCLUSIONS

In PLWH, marijuana smoking was associated with higher lung volumes and potentially with radiographic emphysema. No consistently negative associations were observed between marijuana and measures of chronic lung health.

[Asthma and cannabis, cocaine or heroin use]

INTRODUCTION

The use of cannabis, cocaine or heroin can be responsible for many respiratory complications including asthma.

OBJECTIVES

The aim of this systematic literature review of data was to expose the relations between cannabis, cocaine or heroin use and asthma.

RESULTS

Cannabis, cocaine or heroin use by inhalation may be responsible for respiratory symptoms (cough, wheezing), asthma onset, acute asthma exacerbations (which may require intubation and invasive ventilation) or deaths related to asthma. Lower adherence to asthma treatment is also observed. Cannabis induces a rapid bronchodilator effect. In contrast, its chronic use may induce a decrease in specific airway conductance. Studies on forced expiratory volume in one second (FEV1) reduction or decline are discordant.

CONCLUSION

Cannabis, cocaine or heroin use must be considered in cases of acute respiratory symptoms or asthma exacerbation in young persons and practitioners must help illicit substance users to stop their consumption.

The effects of marijuana smoking on lung function in older people

BACKGROUND

Previous studies have associated marijuana exposure with increased respiratory symptoms and chronic bronchitis among long-term cannabis smokers. The long-term effects of smoked marijuana on lung function remain unclear.

METHODS

We determined the association of marijuana smoking with the risk of spirometrically defined chronic obstructive pulmonary disease (COPD) (post-bronchodilator forced expiratory volume in 1 s (FEV₁)/forced vital capacity ratio <0.7) in 5291 population-based individuals and the rate of decline in FEV₁ in a subset of 1285 males and females, aged ≥40 years, who self-reported use (or non-use) of marijuana and tobacco cigarettes and performed spirometry before and after inhaled bronchodilator on multiple occasions. Analysis for the decline in FEV₁ was performed using random mixed effects regression models adjusted for age, sex and body mass index. Heavy tobacco smoking and marijunana smoking was defined as >20 pack-years and >20 joint-years, respectively.

RESULTS

∼20% of participants had been or were current marijuana smokers with most having smoked tobacco cigarettes in addition (83%). Among heavy marijuana users, the risk of COPD was significantly increased (adjusted OR 2.45, 95% CI 1.55-3.88). Compared to never-smokers of marijuana and tobacco, heavy marijuana smokers and heavy tobacco smokers experienced a faster decline in FEV₁ by 29.5 mL·year^-1 (p=0.0007) and 21.1 mL·year^-1 (p<0.0001), respectively. Those who smoked both substances experienced a decline of 32.31 mL·year^-1 (p<0.0001).

INTERPRETATION

Heavy marijuana smoking increases the risk of COPD and accelerates FEV₁ decline in concomitant tobacco smokers beyond that observed with tobacco alone.

The Impact of Perioperative Cannabis Use: A Narrative Scoping Review

As countries progressively embrace the legalization of both medicinal and recreational cannabis, there remains a significant knowledge gap when it comes to the perioperative uses of cannabis, as well as the management of cannabis users. This review summarizes the information available on the subject based on existing published studies. Articles outlining the physiological changes occurring in the human body during acute and chronic use of cannabis (outside the context of anesthesia) are also taken into consideration as understanding these changes allows a more calculated approach to better anticipate patients' needs in the perioperative setting. Common questions facing the anesthesiologist at each phase of the perioperative period will be addressed and a systematic approach to the effect of cannabinoids on various organ systems will also be presented. Issues unique to cannabis use such as cannabis withdrawal syndrome and alterations in post-operative pain processing will also be discussed. To date, the number of studies available for guidance is small and study designs are markedly heterogenous, if not limited, making conclusions challenging. While the currently available information can assist in making decisions, further studies of larger scale are eagerly anticipated to help guide future patient care.

Pulmonary effects of inhaled cannabis smoke

Background: The smoke generated from cannabis delivers biologically active cannabinoids and a number of combustion-derived toxins, both of which raise questions regarding the impact of cannabis smoking on lung function, airway inflammation and smoking-related lung disease.Objectives: Review the potential effects of cannabis smoking on respiratory symptoms, lung function, histologic/molecular alterations in the bronchial mucosa, smoking-related changes in alveolar macrophage function and the potential clinical impact of cannabis smoking on chronic obstructive pulmonary disease, lung cancer and pulmonary infections.Methods: Focused literature review.Results: The carcinogens and respiratory toxins in cannabis and tobacco smoke are similar but the smoking topography for cannabis results in higher per-puff exposures to inhaled tar and gases. The frequency of chronic cough, sputum and wheeze and the presence of airway mucosal inflammation, goblet cell and vascular hyperplasia, metaplasia and cellular disorganization are similar between cannabis smokers and tobacco smokers. Cannabis smoke has modest airway bronchodilator properties but of unclear clinical significance. While clear evidence exists for progression to obstructive lung disease and emphysema in chronic tobacco smokers, the effects from habitual cannabis use are less clear. Evidence suggests that alveolar macrophages from cannabis smokers have deficits in cytokine production and antimicrobial activity not present in cells from tobacco smokers.Conclusions: Solid conclusions regarding the respiratory consequences of regular cannabis smoking are difficult to make due to a relative paucity of literature, confounding by concurrent tobacco smoking and reports of conflicting outcomes. Additional well-controlled clinical studies on the pulmonary consequences of habitual cannabis use are needed.

Marijuana and the lung: hysteria or cause for concern?

Increasing cannabis use and legalisation highlights the paucity of data we have on the safety of cannabis smoking for respiratory health. Unfortunately, concurrent use of tobacco among marijuana smokers makes it difficult to untangle individual effect of marijuana smoking. Chronic cannabis only smoking has been shown in large cohort studies to reduce forced expiratory volume in 1 s/forced vital capacity via increasing forced vital capacity in chronic use contrary to the picture seen in tobacco smoking. The cause of this is unclear and there are various proposed mechanisms including respiratory muscle training secondary to method of inhalation and acute anti-inflammatory effect and bronchodilation of cannabis on the airways. While cannabis smoke has been shown to increase symptoms of chronic bronchitis, it has not been definitively shown to be associated with shortness of breath or irreversible airway changes. The evidence surrounding the development of lung cancer is less clear; however, preliminary evidence does not suggest association. Bullous lung disease associated with marijuana use has long been observed in clinical practice but published evidence is limited to a total of 57 published cases and only one cross-sectional study looking at radiological changes among chronic users which did not report any increase in macroscopic emphysema. More studies are required to elucidate these missing points to further guide risk stratification, clinical diagnosis and management.

Key points

Cannabis smoking has increased and is likely to increase further with relaxation of legalisation and medicinal use of cannabinoids.Chronic marijuana smoking often produces symptoms similar to those of chronic tobacco smoking such as cough, sputum production, shortness of breath and wheeze.Cessation of marijuana smoking is associated with a reduction in respiratory symptoms and no increased risk of chronic bronchitis.Spirometry changes seen in chronic marijuana smokers appear to differ from those in chronic tobacco smokers. In chronic marijuana smokers there is an increase in FVC as opposed to a definite decrease in FEV₁.Multiple case series have demonstrated peripheral bullae in marijuana smokers, but no observational studies have elucidated the risk.There is currently no clear association between cannabis smoking and lung cancer, although the research is currently limited.

Educational aims

To update readers on legalisation of recreational and medicinal cannabis.To summarise the evidence base surrounding the respiratory effects of inhaled marijuana use.To provide clinicians with an understanding of the main differences between cannabis and tobacco to be able to apply this to patient education.To highlight common respiratory problems among cannabis users and the need for recreational drug history taking.

Marijuana Use, Respiratory Symptoms, and Pulmonary Function: A Systematic Review and Meta-analysis

Background

The health effects of smoking marijuana are not well-understood.

Purpose

To examine the association between marijuana use and respiratory symptoms, pulmonary function, and obstructive lung disease among adolescents and adults.

Data Sources

PubMed, Embase, PsycINFO, MEDLINE, and the Cochrane Library from 1 January 1973 to 30 April 2018.

Study Selection

Observational and interventional studies published in English that reported pulmonary outcomes of adolescents and adults who used marijuana.

Data Extraction

Four reviewers independently extracted study characteristics and assessed risk of bias. Three reviewers assessed strength of evidence. Studies of similar design with low or moderate risk of bias and sufficient data were pooled.

Data Synthesis

Twenty-two studies were included. A pooled analysis of 2 prospective studies showed that marijuana use was associated with an increased risk for cough (risk ratio [RR], 2.04 [95% CI, 1.02 to 4.06]) and sputum production (RR, 3.84 [CI, 1.62 to 9.07]). Pooled analysis of cross-sectional studies (1 low and 3 moderate risk of bias) showed that marijuana use was associated with cough (RR, 4.37 [CI, 1.71 to 11.19]), sputum production (RR, 3.40 [CI, 1.99 to 5.79]), wheezing (RR, 2.83 [CI, 1.89 to 4.23]), and dyspnea (RR, 1.56 [CI, 1.33 to 1.83]). Data on pulmonary function and obstructive lung disease were insufficient.

Limitation

Few studies were at low risk of bias, marijuana exposure was limited in the population studied, cohorts were young overall, assessment of marijuana exposure was not uniform, and study designs varied.

Conclusion

Low-strength evidence suggests that smoking marijuana is associated with cough, sputum production, and wheezing. Evidence on the association between marijuana use and obstructive lung disease and pulmonary function is insufficient.

Primary Funding Source

None. (PROSPERO: CRD42017059224).

Marijuana and Lung Disease

As marijuana smoking prevalence increases in the United States, concern regarding its potential risks to lung health has also risen, given the general similarity in the smoke contents between marijuana and tobacco. Most studies have found a significant association between marijuana smoking and chronic bronchitis symptoms after adjustment for tobacco. Although reports are mixed regarding associations between marijuana smoking and lung function, none have shown a relationship to decrements in FEV₁ and few have found a relationship to a decreased ratio of FEV₁/FVC, possibly related to an association between marijuana and an increased FVC. A few studies have found a modest reduction in specific airway conductance in relation to marijuana, probably reflecting endoscopic evidence of bronchial mucosal edema among habitual marijuana smokers. Diffusing capacity in marijuana smokers has been normal, and two studies of thoracic high-resolution CT scan have not shown any association of marijuana smoking with emphysema. Although bronchial biopsies from habitual marijuana smokers have shown precancerous histopathologic changes, a large cohort study and a pooled analysis of six well-designed case-control studies have not found evidence of a link between marijuana smoking and lung cancer. The immunosuppressive effects of delta-9 tetrahydrocannabinol raise the possibility of an increased risk of pneumonia, but further studies are needed to evaluate this potential risk. Several cases series have demonstrated pneumothoraces/pneumomediastinum and bullous lung disease in marijuana smokers, but these associations require epidemiologic studies for firmer evidence of possible causality.

Effect of cannabis smoking on lung function and respiratory symptoms: a structured literature review

As cannabis use increases, physicians need to be familiar with the effects of both cannabis and tobacco on the lungs. However, there have been very few long-term studies of cannabis smoking, mostly due to legality issues and the confounding effects of tobacco. It was previously thought that cannabis and tobacco had similar long-term effects as both cause chronic bronchitis. However, recent large studies have shown that, instead of reducing forced expiratory volume in 1 s and forced vital capacity (FVC), marijuana smoking is associated with increased FVC. The cause of this is unclear, but acute bronchodilator and anti-inflammatory effects of cannabis may be relevant. Bullous lung disease, barotrauma and cannabis smoking have been recognised in case reports and small series. More work is needed to address the effects of cannabis on lung function, imaging and histological changes.

Recent Marijuana Use and Associations With Exhaled Nitric Oxide and Pulmonary Function in Adults in the United States

BACKGROUND

The medical and recreational use of marijuana is now legal in some parts of the United States; the health effects are unknown. We aimed to evaluate associations between recent marijuana use and exhaled nitric oxide (eNO) and pulmonary function.

METHODS

We performed a cross-sectional study of 10,327 US adults participating in the National Health and Nutrition Examination Survey in the years 2007 to 2012. We examined associations between marijuana use and eNO, FEV1, FVC, the FEV1/FVC ratio, and forced expiratory flow (midexpiratory phase) (FEF25%-75%) by weighted linear regression.

RESULTS

In the study population, there were 4,797 never users, 4,084 past marijuana users, 555 participants who used marijuana 5 to 30 days before the examination, and 891 participants who used marijuana 0 to 4 days before the examination. Current marijuana use in the past 4 days was associated with 13% lower eNO (95% CI, -18% to 8%). FVC was higher in past users (75 mL; 95% CI, 38-112) and current users in the past 5 to 30 days (159 mL; 95% CI, 80-237) and in users within 0 to 4 days of the examination (204 mL; 95% CI, 139-270) compared with never users. All associations remained unchanged and statistically significant in sensitivity analyses excluding current and past tobacco users.

CONCLUSIONS

Current marijuana use was associated with lower levels of eNO and higher FVC. The lower eNO in marijuana smokers suggests that short-term exposure to marijuana may, like tobacco, acutely affect the pulmonary vascular endothelium and impair airflow through the small airways.

The effects of marijuana exposure on expiratory airflow. A study of adults who participated in the U.S. National Health and Nutrition Examination Study

RATIONALE

Given the inconclusive science on the long-term effects of marijuana exposure on lung function, the increasing tetrahydrocannabinol composition of marijuana over time, and the increasing legal accessibility of the substance, continued investigation is needed.

OBJECTIVES

To determine the independent association between recent and chronic marijuana smoke exposure with spirometric parameters of lung function and symptoms of respiratory health in a large cohort of U.S. adults.

METHODS

This is a cross-sectional study of U.S. adults who participated in the National Health and Nutrition Examination Survey cycles from 2007-2008 and 2009-2010, using the data from standardized spirometry and survey questions performed during these years.

MEASUREMENTS AND MAIN RESULTS

In the combined 2007-2010 cohort, 59.1% replied that they had used marijuana at least once, and 12.2% had used in the past month. For each additional day of marijuana use in the prior month, there were no changes in percent predicted FEV1 (0.002 ± 0.04%; P = 0.9), but there was an associated increase in percent predicted FVC (0.13 ± 0.03%, P = 0.0001) and decrease in the FEV1/FVC ratio (-0.1 ± 0.04%; P < 0.0001). In multivariable regressions, 1-5 and 6-20 joint-years of marijuana use were not associated with an FEV1/FVC less than 70% (odds ratio [OR] = 1.1, 95% confidence interval [CI] = 0.7-1.6, P = 0.8, and OR = 1.2, 95% CI = 0.8-1.8, P = 0.4, respectively), whereas over 20 joint-years was associated with an FEV1/FVC less than 70% (OR = 2.1; 95% CI = 1.1-3.9; P = 0.02). For each additional marijuana joint-year smoked, there was no associated change in the mean percent predicted FEV1 (0.02 ± 0.02%; P = 1.00), an increase in percent predicted FVC (0.07 ± 0.02%; P = 0.004), and a decrease in FEV1/FVC (-0.03 ± 0.01%; P = 0.02).

CONCLUSIONS

In a large cross-section of U.S. adults, cumulative lifetime marijuana use, up to 20 joint-years, is not associated with adverse changes in spirometric measures of lung health. Although greater than 20 joint-years of cumulative marijuana exposure was associated with a twofold increased odds of a FEV1/FVC less than 70%, this was the result of an increase in FVC, rather than a disproportional decrease in FEV1 as is typically associated with obstructive lung diseases.

Legalizing Cannabis: A physician's primer on the pulmonary effects of marijuana

Habitual smoking of marijuana is associated with multiple respiratory symptoms such as cough, sputum production, and wheezing .These symptoms are not significantly different from those exhibited by tobacco smokers. Furthermore, endobronchial biopsies of habitual smokers of marijuana and /or tobacco have shown that both marijuana and cigarette smoking cause significant bronchial mucosal histopathology and that these effects are additive. Although marijuana smokers have minimal changes in pulmonary function studies as compared to tobacco smokers, they may develop bullous disease and spontaneous pneumothoraces. The relationship between marijuana smoking and lung cancer remains unclear due to design limitations of the studies published so far. These findings should warn individuals that marijuana smoking may result in serious short-term and long-term respiratory complications, and habitual marijuana use should be viewed with caution. The medical literature so far does not support routine evaluation by pulmonary function tests or imaging studies; until more definitive data is available, we do not recommend the regular use of these tests in the evaluation of habitual marijuana smokers.

Cannabis smoking and respiratory health: consideration of the literature

The respiratory health effects from tobacco smoking are well described. Cannabis smoke contains a similar profile of carcinogenic chemicals as tobacco smoke but is inhaled more deeply. Although cannabis smoke is known to contain similar harmful and carcinogenic substances to tobacco smoke, relatively little is understood regarding the respiratory health effects from cannabis smoking. There is a need to integrate research on cannabis and respiratory health effects so that gaps in the literature can be identified and the more consistent findings can be consolidated with the purpose of educating smokers and health service providers. This review focuses on several aspects of respiratory health and cannabis use (as well as concurrent cannabis and tobacco use) and provides an update to (i) the pathophysiology; (ii) general respiratory health including symptoms of chronic bronchitis; and (iii) lung cancer.

[Cannabis use and impairment of respiratory function]

Cannabis is the most commonly smoked illicit substance in many countries including France. It can be smoked alone in plant form (marijuana) but in our country it is mainly smoked in the form of cannabis resin mixed with tobacco. The technique of inhaling cannabis differs from that of tobacco, increasing the time that the smoke spends in contact with the bronchial mucosal and its impact on respiratory function. One cigarette composed of cannabis and tobacco is much more harmful than a cigarette containing only tobacco. In cannabis smokers there is an increased incidence of respiratory symptoms and episodes of acute bronchitis. Cannabis produces a rapid bronchodilator effect; chronic use provokes a reduction in specific conductance and increase in airways resistance. Studies on the decline of Forced Expiratory Volume are discordant. Cannabis smoke and tetrahydrocannabinol irritate the bronchial tree. They bring about histological signs of airways inflammation and alter the fungicidal and antibacterial activity of alveolar macrophages. Inhalation of cannabis smoke is a risk factor for lung cancer. Stopping smoking cannabis will bring about important benefits for lung function. This should encourage clinicians to offer patients support in quitting smoking.

Impact of changes in regular use of marijuana and/or tobacco on chronic bronchitis

We sought to evaluate possible changes in the prevalence of chronic bronchitis in relation to continuing or changing smoking status for marijuana and/or tobacco. For this purpose we followed 299 participants in a longitudinal cohort study of the impact of heavy habitual use of marijuana alone or with tobacco on respiratory symptoms over a mean of 9.8 years during which subjects underwent repeated administration of a detailed drug use and respiratory questionnaire at intervals of ≥1 yr. Using logistic regression, we calculated odds ratios to assess the relationship between chronic bronchitic symptoms and smoking status for marijuana and tobacco at the first visit (current smoking versus never smoking) and at the last follow-up visit (continuing smoking versus, separately, never smoking and former smoking). We found that continuing smokers of either marijuana or tobacco had a significantly increased likelihood of having chronic bronchitis at follow-up compared to both never smokers and former smokers. On the other hand, former smokers of either substance were no more likely to have chronic respiratory symptoms at follow-up than never smokers. These findings demonstrate the benefit of marijuana smoking cessation in resolving pre-existing symptoms of chronic bronchitis.

Association between marijuana exposure and pulmonary function over 20 years

CONTEXT

Marijuana smoke contains many of the same constituents as tobacco smoke, but whether it has similar adverse effects on pulmonary function is unclear.

OBJECTIVE

To analyze associations between marijuana (both current and lifetime exposure) and pulmonary function.

DESIGN, SETTING, AND PARTICIPANTS

The Coronary Artery Risk Development in Young Adults (CARDIA) study, a longitudinal study collecting repeated measurements of pulmonary function and smoking over 20 years (March 26, 1985-August 19, 2006) in a cohort of 5115 men and women in 4 US cities. Mixed linear modeling was used to account for individual age-based trajectories of pulmonary function and other covariates including tobacco use, which was analyzed in parallel as a positive control. Lifetime exposure to marijuana joints was expressed in joint-years, with 1 joint-year of exposure equivalent to smoking 365 joints or filled pipe bowls.

MAIN OUTCOME MEASURES

Forced expiratory volume in the first second of expiration (FEV(1)) and forced vital capacity (FVC).

RESULTS

Marijuana exposure was nearly as common as tobacco exposure but was mostly light (median, 2-3 episodes per month). Tobacco exposure, both current and lifetime, was linearly associated with lower FEV(1) and FVC. In contrast, the association between marijuana exposure and pulmonary function was nonlinear (P < .001): at low levels of exposure, FEV(1) increased by 13 mL/joint-year (95% CI, 6.4 to 20; P < .001) and FVC by 20 mL/joint-year (95% CI, 12 to 27; P < .001), but at higher levels of exposure, these associations leveled or even reversed. The slope for FEV(1) was -2.2 mL/joint-year (95% CI, -4.6 to 0.3; P = .08) at more than 10 joint-years and -3.2 mL per marijuana smoking episode/mo (95% CI, -5.8 to -0.6; P = .02) at more than 20 episodes/mo. With very heavy marijuana use, the net association with FEV(1) was not significantly different from baseline, and the net association with FVC remained significantly greater than baseline (eg, at 20 joint-years, 76 mL [95% CI, 34 to 117]; P < .001).

CONCLUSION

Occasional and low cumulative marijuana use was not associated with adverse effects on pulmonary function.

Effects of smoking cannabis on lung function

Although cannabis (or marijuana) is the world's most widely-used illicit drug, there has been surprisingly little research into its effects on respiratory health. Part of the problem is the inherent difficulty of studying the long-term effects of an illegal habit. It has often been assumed that smoking cannabis will have similar long-term effects to smoking tobacco. Several recent observational studies suggest that this is not the case and that cannabis has quite different effects on the lung function. There are consistent findings that smoking cannabis is associated with large airway inflammation, symptoms of bronchitis, increased airway resistance and lung hyperinflation. The evidence that smoking cannabis leads to features of chronic obstructive pulmonary disease, such as airflow obstruction and emphysema is not convincing. However, there are numerous case reports of bullous emphysema among cannabis smokers. These findings have not been confirmed in systematic analytical studies and probably represent uncommon adverse effects in very heavy cannabis smokers. There is now additional controversial evidence that cannabis is at least an occasional cause of respiratory malignancies, but again the evidence is inconclusive.

The human toxicity of marijuana: a critique of a review by Nahas and Latour

A review entitled "The human toxicity of marijuana" was published in 1992 in the Medical Journal of Australia. The authors claimed that the adverse effects of cannabis use have been trivialized and that the effects are much more serious than earlier reported. We have made a careful study of this review and examined the claims made. We compared the claims of the authors with the information contained in the documents they cited and found that at least 28 of the 35 citations in this article were cited inaccurately. Five of these publications were misquoted, or the findings of the study were not fully reported. Twenty-three citations contained other errors, leaving only six to eight (two citations could not be retrieved because of their obscurity) accurate citations among 35. All of these inaccuracies operate in the direction of finding an adverse effect of marijuana.

Ammonia release from heated 'street' cannabis leaf and its potential toxic effects on cannabis users

AIMS

To use selected ion flow tube mass spectrometry (SIFT-MS) to analyse the molecular species emitted by heated 'street' cannabis plant material, especially targeting ammonia.

MATERIALS AND METHODS

Samples of 'street' cannabis leaf, held under a UK Home Office licence, were prepared by finely chopping and mixing the material. The samples were then heated in commercially available devices. The air containing the released gaseous compounds was sampled into the SIFT-MS instrument for analysis. Smoke from standard 3% National Institute on Drug Abuse (NIDA) cannabis cigarettes was also analysed.

FINDINGS

For 'street' cannabis, ammonia was present in the air samples from the devices at levels approaching 200 parts per million (p.p.m.). This is compared with peak levels of 10 p.p.m. using NIDA samples of known provenance and tetrahydrocannabinol content (3%). Several other compounds were present at lower levels, including acetaldehyde, methanol, acetone, acetic acid and uncharacterized terpenes.

CONCLUSIONS

Awareness of the risks of inhaling the smoke directly from burning cannabis has led to the development of a number of alternative methods of delivery, which are claimed to be safer than direct smoking. Ammonia at toxic levels is produced from heating 'street' cannabis in these commercially available devices. Thus, the use of these devices to deliver 'street' cannabis is now open to question and further research is needed to investigate their safety.

Cannabinoids in health and disease

Cannabis sativa L. preparations have been used in medicine for millenia. However, concern over the dangers of abuse led to the banning of the medicinal use of marijuana in most countries in the 1930s. Only recently, marijuana and individual natural and synthetic cannabinoid receptor agonists and antagonists, as well as chemically related compounds, whose mechanism of action is still obscure, have come back to being considered of therapeutic value. However, their use is highly restricted. Despite the mild addiction to cannabis and the possible enhancement of addiction to other substances of abuse, when combined with cannabis, the therapeutic value of cannabinoids is too high to be put aside. Numerous diseases, such as anorexia, emesis, pain, inflammation, multiple sclerosis, neurodegenerative disorders (Parkinson's disease, Huntington's disease, Tourette's syndrome, Alzheimer's disease), epilepsy, glaucoma, osteoporosis, schizophrenia, cardiovascular disorders, cancer, obesity, and metabolic syndrome-related disorders, to name just a few, are being treated or have the potential to be treated by cannabinoid agonists/antagonists/cannabinoid-related compounds. In view of the very low toxicity and the generally benign side effects of this group of compounds, neglecting or denying their clinical potential is unacceptable--instead, we need to work on the development of more selective cannabinoid receptor agonists/antagonists and related compounds, as well as on novel drugs of this family with better selectivity, distribution patterns, and pharmacokinetics, and--in cases where it is impossible to separate the desired clinical action and the psychoactivity--just to monitor these side effects carefully.

Forensic Lung Pathology

Sudden and unexpected natural deaths and nonnatural deaths may result from various pulmonary conditions. Additionally, several nonpulmonary conditions of forensic significance may be complicated by the development of respiratory lesions. Certain situations with pulmonary pathology are particularly likely to be critically scrutinized and may form the basis of allegations of medical negligence, other personal injury liability, or wrongful death.1

Effects of marijuana smoking on pulmonary function and respiratory complications: a systematic review

BACKGROUND

The relationship between marijuana smoking and pulmonary function or respiratory complications is poorly understood; therefore, we conducted a systematic review of the impact of marijuana smoking on pulmonary function and respiratory complications.

METHODS

Studies that evaluated the effect of marijuana smoking on pulmonary function and respiratory complications were selected from the MEDLINE, PsychINFO, and EMBASE databases according to predefined criteria from January 1, 1966, to October 28, 2005. Two independent reviewers extracted data and evaluated study quality based on established criteria. Study results were critically appraised for clinical applicability and research methods.

RESULTS

Thirty-four publications met selection criteria. Reports were classified as challenge studies if they examined the association between short-term marijuana use and airway response; other reports were classified as studies of long-term marijuana smoking and pulmonary function or respiratory complications. Eleven of 12 challenge studies found an association between short-term marijuana administration and bronchodilation (eg, increases of 0.15-0.25 L in forced expiratory volume in 1 second). No consistent association was found between long-term marijuana smoking and airflow obstruction measures. All 14 studies that assessed long-term marijuana smoking and respiratory complications noted an association with increased respiratory symptoms, including cough, phlegm, and wheeze (eg, odds ratio, 2.00; 95% confidence interval, 1.32-3.01, for the association between marijuana smoking and cough). Studies were variable in their overall quality (eg, controlling for confounders, including tobacco smoking).

CONCLUSIONS

Short-term exposure to marijuana is associated with bronchodilation. Physiologic data were inconclusive regarding an association between long-term marijuana smoking and airflow obstruction measures. Long-term marijuana smoking is associated with increased respiratory symptoms suggestive of obstructive lung disease.

A peek into Pandora's box: the medical excuse marijuana controversy

The smoking of marijuana for medicinal applications is a volatile and difficult issue for the medical and regulatory communities which has reached the forefront of discussions of public policy. Any consideration of this issue must take into account the substantial toxicity, impurity, and morbidity associated with marijuana use. Several states have passed ballot initiatives or legislation that allow a medical excuse for possession of marijuana. These initiatives bypass the Food and Drug Administration process of proving safety and efficacy, and they have created serious regulatory dilemmas for state regulatory boards. Several examinations of the issue have consistently drawn question to the validity of smoking an impure substance while voicing concern for the well being of patients in need. The historical, social, medical, and legal issues are examined.

Respiratory health effects of cannabis: position statement of the Thoracic Society of Australia and New Zealand

Both the gaseous and the particulate phases of tobacco and cannabis smoke contain a similar range of harmful chemicals. However, differing patterns of inhalation mean that smoking a 'joint' of cannabis results in exposure to significantly greater amounts of combusted material than with a tobacco cigarette. The histopathological effects of cannabis smoke exposure include changes consistent with acute and chronic bronchitis. Cellular dysplasia has also been observed, suggesting that, like tobacco smoke, cannabis exposure has the potential to cause malignancy. These features are consistent with the clinical presentation. Symptoms of cough and early morning sputum production are common (20-25%) even in young individuals who smoke cannabis alone. Almost all studies indicate that the effects of cannabis and tobacco smoking are additive and independent. Public health education should dispel the myth that cannabis smoking is relatively safe by highlighting that the adverse respiratory effects of smoking cannabis are similar to those of smoking tobacco, even although it remains to be confirmed that smoking cannabis alone leads to the development of chronic lung disease.

A longitudinal study of the effects of tobacco and cannabis exposure on lung function in young adults

AIM

To assess the possible effects of tobacco and cannabis smoking on lung function in young adults between the ages of 18 and 26.

SETTING AND PARTICIPANTS

A group of over 900 young adults derived from a birth cohort of 1037 subjects born in Dunedin, New Zealand in 1972/73 were studied at age 18, 21 and 26 years.

MEASUREMENTS

Cannabis and tobacco smoking were documented at each age using a standardized interview. Lung function, as measured by the forced expiratory volume in one second/vital capacity (FEV1/VC) ratio, was obtained by simple spirometry. A fixed effects regression model was used to analyse the data to take account of confounding factors.

FINDINGS

When the sample was stratified for cumulative use, there was evidence of a linear relationship between cannabis use and FEV1/VC (P < 0.05). In the absence of adjusting for other variables, increasing cannabis use over time was associated with a decline in FEV1/VC with time; the mean FEV1/VC among subjects using cannabis on 900 or more occasions was 7.2%, 2.6% and 5.0% less than non-users at ages 18, 21 and 26, respectively. After controlling for potential confounding factors (age, tobacco smoking and weight) the negative effect of cumulative cannabis use on mean FEV1/VC was only marginally significant (P < 0.09). Age (P < 0.001), cigarette smoking (P < 0.05) and weight (P < 0.001) were all significant predictors of FEV1/VC. Cannabis use and daily cigarette smoking acted additively to influence FEV1/VC.

CONCLUSIONS

Longitudinal observations over 8 years in young adults revealed a dose-dependent relationship between cumulative cannabis consumption and decline in FEV1/VC. However, when confounders were accounted for the effect was reduced and was only marginally significant, but given the limited time frame over which observations were made, the trend suggests that continued cannabis smoking has the potential to result in clinically important impairment of lung function.

Medicinal marijuana: a comprehensive review

Considerable controversy exists regarding the role of marijuana as a therapeutic agent; however, many practitioners are taught very little about existing marijuana data. The authors therefore undertook a comprehensive literature review of the topic. References were identified using textbooks, review and opinion articles, and a primary literature review in MEDLINE. Sources were included in this review based primarily on the quality of the data. Some data exists that lends credence to many of the claims about marijuana's properties. In general, however, the body of literature about marijuana is extremely poor in quality. Marijuana and/or its components may help alleviate suffering in patients with a variety of serious illnesses. Health care providers can best minimize short term adverse consequences and drug interactions for terminally ill patients by having a thorough understanding of the pharmacology of marijuana, potential adverse reactions, infection risks, and drug interactions (along with on-going monitoring of the patient). For chronic conditions, the significance and risk of short and long term adverse effects must be weighed against the desired benefit. Patients who are best suited to medicinal marijuana will be those who will gain substantial benefit to offset these risks, and who have failed a well-documented, compliant and comprehensive approach to standard therapies.

Comparative effects of alcohol and marijuana on mood, memory, and performance

This study compared subjective and behavioral effect profiles of alcohol and smoked marijuana using technology that controlled puffing and inhalation parameters. Male volunteers (n = 5) with histories of moderate alcohol and marijuana use were administered three doses of alcohol (0.25, 0.5, or 1.0 g/kg), three doses of marijuana [4.8, or 16 puffs of 3.55% delta 9-tetrahydrocannabinol (THC)], and placebo in random order under double blind conditions in seven separate sessions. Blood alcohol concentration (10-90 mg/dl) and THC levels (63-188 ng/ml) indicated that active drug was delivered to subjects dose dependently. Alcohol and marijuana produced dose-related changes in subjective measures of drug effect. Ratings of perceived impairment were identical for the high doses of alcohol and marijuana. Both drugs produced comparable impairment in digit-symbol substitution and word recall tests, but had no effect in time perception and reaction time tests. Alcohol, but not marijuana, slightly impaired performance in a number recognition test. These data are useful for understanding the relative performance impairment produced by alcohol and marijuana at the delivered doses and the relationship between their subjective and behavioral effects.

Lymphocytic subpopulation profiles in bronchoalveolar lavage fluid and peripheral blood from tobacco and marijuana smokers

The effect of heavy, habitual marijuana use compared with tobacco smoking on the composition of bronchoalveolar and peripheral blood lymphocytic phenotypes was examined. Bronchoalveolar lavage (BAL) and peripheral blood (PB) samples were taken from 14 nonsmokers (NS), 14 tobacco smokers (TS), 19 heavy, habitual marijuana smokers (MS), and 9 marijuana and tobacco smokers (MTS). In BAL fluid, marijuana use was associated with significantly higher alveolar macrophage concentrations, whereas tobacco smoking was associated with significantly higher alveolar macrophage, as well as higher bronchoalveolar lymphocyte and neutrophil concentrations. The bronchoalveolar T-lymphocytic phenotypic profiles of marijuana users differed from those of tobacco smokers. Tobacco, not marijuana, was found to have a significant effect toward lower percentages of bronchoalveolar CD4 cells, toward higher concentrations of bronchoalveolar CD8 cells, and toward lower bronchoalveolar CD4:CD8 ratios. Marijuana use had a significant effect toward lower percentages of bronchoalveolar CD8 cells. In peripheral blood, marijuana, but not tobacco, use was associated with significantly higher percentages of CD4 cells, lower percentages of CD8 cells, and higher CD4:CD8 ratios. These findings suggest that tobacco and marijuana have effects on bronchoalveolar and peripheral blood immunoregulatory T-lymphocytic subpopulations that differ in type or magnitude.

Lung cancer in patients with human immunodeficiency virus infection compared with historic control subjects

Lung cancer infrequently may be associated with human immunodeficiency virus (HIV) infection. This retrospective case-control study was undertaken to determine if there were differences in age, sex, and stage distribution and in survival between HIV-positive and HIV-indeterminate lung cancer patients. We compared 19 patients with both pathologically verified lung cancer and HIV infection proved by serologic study with lung cancer patients with an indeterminate HIV status. All 19 HIV-positive lung cancer patients were men. This was significantly (p = 0.004) different from the 69 percent male preponderance in 1,335 HIV-indeterminate lung cancer patients. Median ages of HIV-positive and HIV-indeterminate patients were 48 and 61 years, respectively. HIV-positive patients were significantly (p = 0.0139) younger. Stage distribution was similar in both groups. Histologic features and smoking were not significantly different between the two groups. Survival data that were available in 16 HIV-positive patients were compared with 32 HIV-indeterminate control subjects matched for stage, age, sex, and race. The median survival was three months in the HIV-positive group and ten months in the HIV-indeterminate cohort. The survival was significantly different (p = 0.002). There were no one-year survivors in HIV-positive lung cancer patients.

Marijuana and tobacco smoke gas-phase cytotoxins

To evaluate the in vivo versus in vitro paradoxical effects of marijuana and tobacco smoke on pulmonary defenses, the responses to smoke constituents were assessed with an alveolar macrophage tissue culture bioassay. A dose-response impairment of macrophage bactericidal activity was associated with water-soluble, gas-phase constituents. A model airway surface was constructed to examine the behavior of specific gas-phase constituents removed as they passed over wetted surfaces simulating the characteristics of the human respiratory system. Chemical analyses in the bioassay flask and in the model airway were compared. Gas-phase cytotoxins were measured after passage over wetted surface areas analogous to the trachea between the larynx and second-order bronchus. A wetted surface comparable to only 5% of the human airway, or less than 0.05% of the gas-exchanging surface of the entire lung, was capable of complete detoxification of the highly water-soluble gas-phase cytotoxins. In conclusion, gas-phase cytotoxins demonstrable by in vitro bioassays may have no cytotoxic potential when inhaled by humans.

Marijuana smoking and carcinoma of the tongue. Is there an association?

There is considerable theoretical evidence that marijuana should be carcinogenic. However, most reviews have found no direct evidence of chronic marijuana smoking causing lung cancer. Some recent reports implicate marijuana smoking as a cause of cancer of the upper aerodigestive tract, though most of the subjects were exposed to other, possibly confounding, etiologic factors, namely tobacco and alcohol. We report two cases of squamous cell carcinoma of the tongue in men who chronically smoked marijuana but had no other risk factors. The totality of cases may point to a predilection of marijuana smoke for carcinogenesis in the upper aerodigestive tract. This correlates with nonmalignant effects and may be related to a different method of smoking marijuana compared with tobacco.

Heroin inhalation and asthma

Opiate addiction is an increasing social problem, and there has been a change from taking opiates intravenously to inhaling them in many areas of Britain. Three patients with asthma who required mechanical ventilation soon after heroin inhalation were described. Two subsequently died of acute severe asthma. The patients were reluctant to admit to their addiction and persisted inhaling heroin despite medical advice and counselling. Opiate inhalation can provoke life threatening asthmatic attacks and should be considered in patients at risk of abusing drugs who have poorly controlled asthma.