The following is the summary of “Inhaled Marijuana and the Lung” published in the November 2022 issue of Allergy and Clinical Immunology by Tashkin, et al.

Although vaping has become increasingly popular as a technique of inhaling marijuana, it has been linked to a number of cases of acute severe lung injury, sometimes fatal. Smoking remains the most prevalent form of inhaling marijuana and has been examined more extensively. Both healthy people and those with asthma have had a mild but significant increase in bronchodilation after smoking marijuana. 

The following are some of the long-term consequences of regular marijuana use: mild effects on lung function in cross-sectional studies (no significant decrease in FEV1 but mild reductions in FEV1/forced vital capacity ratio, an increase in forced vital capacity and other lung volumes, reductions in specific airway conductance, and variable effects of maximal mid expiratory flow rates and diffusing capacity), and variable effects on the age-related decline, i.e., coughing, sputum production, and wheezing are all symptoms of chronic bronchitis. Despite the existence of procarcinogenic components in marijuana smoke, most cohort and case-control studies have failed to prove that marijuana smoking is a substantial risk factor for lung cancer. 

Further research is needed to determine if there is a link between marijuana use and asthma. Although the main psychoactive component of marijuana, delta-9 tetrahydrocannabinol, has immunomodulatory properties that could theoretically increase the risk of pneumonia, the few available studies on marijuana smokers have failed to find an increased risk of pneumonia in immunocompetent users, although effects in immunosuppressed individuals have been variable.