Technische Universität München

The Entrepreneurial University

Cannabis preparations contain more than 60 cannabinoids, but the major psychoactive component of cannabis is tetrahydrocannabinol (THC). Some of the most serious adverse effects of cannabis (marijuana) smoking are on the respiratory system. For the adverse effects of cannabis smoke on the lungs, effects of THC are perhaps of less importance than the numerous products of combustion to which smokers are exposed. Evidence suggests that the range of adverse effects on the lungs exerted by smoking cannabis is similar to those induced by tobacco smoking. Both the gaseous and the particulate phases of tobacco and cannabis smoke contain a similar range of harmful chemicals (tar content, carcinogens). However, the pulmonary consequences of cannabis smoking may be magnified by the greater deposition of smoke particulates in the lung due to the differing manner in which cannabis is smoked. Smokers typically inhale deeply and hold their breath to ensure maximum absorption of THC. Studies demonstrate that airway inflammation develops even after limited exposure to cannabis smoke. While THC causes modest short-term bronchodilation, cannabis smoke produces a number of long-term pulmonary changes including histopathological evidence of acute and chronic bronchitis. Symptoms of chronic cough and sputum production, and exercise-related dyspnea are common in cannabis smokers. Habitual marijuana smoking is associated with abnormalities in the structure and function of alveolar macrophages potentially predisposing to pulmonary infection.
Cannabis smoke is carcinogenic in vitro and in vivo and is a possible cause of respiratory cancers in regular cannabis smokers. The same histopathological and mutagenic changes thought to be precursors of lung carcinoma have been found in the lungs of chronic cannabis smokers. Case reports have also documented cancers of the upper aerodigestive tract (mouth, tongue, and esophagus) in young adults who have been chronic cannabis smokers, but evidence from epidemiological studies is inconsistent.