Tan WC, Bourbeau J, Aaron SD, et al. - In order to determine how lung function is influenced in the long-term by smoked marijuana, researchers undertook this study with 5,291 population-based people, including a subset of 1,285 men and women (aged 40 years and older) who self-reported use (or nonuse) of marijuana and tobacco cigarettes. They examined the link between marijuana smoking and the risk of spirometrically-defined COPD [post-bronchodilator FEV₁/FVC < 0·7] in 5,291 participants. They also assessed the rate of decline in FEV₁ in the abovementioned subset. Findings revealed an increase in the risk of COPD among heavy marijuana smokers. In concomitant tobacco smokers, heavy marijuana smoking accelerated FEV₁ drop beyond that observed with tobacco alone.