Effects of smoking cannabis on lung function

Abstract

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.

Cannabis, tobacco smoking, and lung function: a cross-sectional observational study in a general practice population

“…In contrast, previous studies have not always found strong or consistent evidence that cannabis smoking has adverse effects on objective measures of COPD such as the FEV1/FVC ratio. 24,25 The present study did find evidence of such effects, over and above those that appeared attributable to the tobacco use of cannabis smokers. It has been suggested that discrepancies in the evidence partly relate to the extent that cannabis use is associated with increased FVC (which may result from repeated pulmonary hyperinflation related to the way cannabis is smoked.…”

“…It has been suggested that discrepancies in the evidence partly relate to the extent that cannabis use is associated with increased FVC (which may result from repeated pulmonary hyperinflation related to the way cannabis is smoked. 25 FVC was notably higher among cannabis users in the present study. Some studies have reported apparent increases in FEV1 associated with cannabis smokers compared with non-smokers.…”

Cannabis for Inflammatory Bowel Disease

“…Smoking carries its own dangers, although for some these may be tolerable if relief of severe chronic pain is achieved. The respiratory side effects of cannabis have not been well studied, but there is strong evidence that cannabis causes bronchial inflammation and respiratory symptoms, and affects lung function [18]. During smoking, the acids are decarboxylated to the active free cannabinoids.…”

Evaluation of the respiratory system of non-alcohol drug addicted patients

“…However, the fact that group I had lower FEV 1 /FVC values can be interpreted as a spirometric reflection of the high rhonchus level found in this group as revealed by physical examination. Studies in the literature have reported that especially marijuana did not lead to a change in FEV 1 while it caused an increase in FVC and did not change or gave way to a decrease in the FEV 1 /FVC ratio [18]. The facts, however, that FEV 1 /FVC is a spirometric datum which decreases gradually by age and the mean age of group I was found to be older and also history of smoking and the higher probability of obstructive pulmonary diseases related to smoking in group I should be taken into consideration during evaluations.…”