People who smoke both tobacco and marijuana may have a particularly high risk of developing chronic obstructive pulmonary disease (COPD). Cigarette smoking is a well-known risk factor for COPD, a group of lung diseases that includes emphysema and chronic bronchitis. To determine the independent and combined ill-effects of tobacco and marijuana smoking on respiratory symptoms, researchers from America surveyed a random sample of 878 Canadian adults aged 40 years and older. Just over half had ever smoked cigarettes, while 45 per cent had ever used marijuana. The researchers performed spirometric testing before and after administration of 200 µg of salbutamol. It was found that compared with non-smokers, people who only smoked cigarettes were 50 percent more likely to have frequent respiratory symptoms and almost three times more likely to have COPD. Meanwhile, men and women who smoked both tobacco and marijuana were more than twice as likely as non-smokers to have frequent respiratory symptoms, if they'd had more than 50 joints over a lifetime. Their risk of COPD was nearly three times higher than non-smokers. The above findings suggest that marijuana and cigarette smoking may promote COPD. The findings were attributed to the speculation that that marijuana smoking sensitises the airways, making them more vulnerable to the adverse effects of tobacco smoking.
Canadian Medical Association Journal
April 2009