Spontaneous Pneumothorax Secondary to Bullous Lung Emphysema Positive for Cannabinoids upon Toxicological Examination

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.

Effects of cannabis smoking on the respiratory system: A state-of-the-art review

The diminished perception of the health risks associated with the consumption of cannabis (marijuana) lead to a progressive increase in its inhalational use in many countries. Cannabis can be smoked through the use of joints, spliffs and blunts, and it can be vaporised with the use of hookah or e-cigarettes. Delta-9 tetrahydrocannabinol (THC) is the main psychoactive component of cannabis smoke but contains numerous other substances. While the recreational use of cannabis smoking has been legalised in several countries, its health consequences have been underestimated and undervalued. The purpose of this review is to critically review the impact of cannabis smoke on the respiratory system. Cannabis smoke irritates the bronchial tree and is strongly associated with symptoms of chronic bronchitis, with histological signs of airway inflammation and remodelling. Altered fungicidal and antibacterial activity of alveolar macrophages, with greater susceptibility to respiratory infections, is also reported. The association with invasive pulmonary aspergillosis in immunocompromised subjects is particularly concerning. Although cannabis has been shown to produce a rapid bronchodilator effect, its chronic use is associated with poor control of asthma by numerous studies. Cannabis smoking also represents a risk factor for the development of bullous lung disease, spontaneous pneumothorax and hypersensitivity pneumonitis. On the other hand, no association with the development of chronic obstructive pulmonary disease was found. Finally, a growing number of studies report an independent association of cannabis smoking with the development of lung cancer. In conclusion, unequivocal evidence established that cannabis smoking is harmful to the respiratory system. Cannabis smoking has a wide range of negative effects on respiratory symptoms in both healthy subjects and patients with chronic lung disease. Given that the most common and cheapest way of assumption of cannabis is by smoking, healthcare providers should be prepared to provide counselling on cannabis smoking cessation and inform the public and decision-makers.