Moderate marijuana smoking is not associated with adverse effects on lung function according to a new medical study. The study, Association Between Marijuana Exposure and Pulmonary Function Over 20 Years, was published in the Journal of the American Medical Association.
While moderate tobacco use has been associated with more lung problems, the study found effectively no link between moderate marijuana use and reduced pulmonary function over the long term. From the JAMA press release on the study:
More than half of participants (54 percent; average age at baseline, 25 years) reported current marijuana smoking, tobacco smoking, or both at 1 or more examinations. The median (midpoint) intensity of tobacco use in tobacco smokers was substantially higher (8-9 cigarettes/day) than the median intensity of marijuana use in marijuana smokers (2-3 episodes in the last 30 days). In fully adjusted models that considered 4-level categorizations of current and lifetime exposure to tobacco and marijuana, tobacco smoking (both current and lifetime) was associated with a lower FEV1 and current smoking with a lower FVC. In contrast, exposure to marijuana (both current and lifetime) was associated with higher FVC and lifetime exposure with higher FEV1. At low lifetime exposure levels, increasing marijuana use was associated with an increase in both FEV1 and FVC. “With up to 7 joint-years of life-time exposure (e.g., 1 joint/day for 7 years or 1 joint/week for 49 years), we found no evidence that increasing exposure to marijuana adversely affects pulmonary function,” the researchers write.
(Emphasis mine. “Lung function was assessed by the measurements of forced expiratory volume in the first second of expiration (FEV1) and forced vital capacity (FVC), with lower measures corresponding to poorer lung function.”)
The study did not contain enough very heavy marijuana smokers to reach a firm conclusion about the impact very heavy marijuana use would have on lung function.