According to recently published clinical trial data in the Journal of the American Medical Association (JAMA), exposure to moderate levels of cannabis smoke, even over the long-term, is not associated with adverse effects on pulmonary function.
The association between marijuana exposure and pulmonary function was analyzed by investigators at the University of California, San Francisco over a 20-year period in a cohort of 5,115 men and women in four US cities.
Researchers “confirmed the expected reductions in FEV1 (forced expiratory volume in the first second of expiration) and FVC (forced vital capacity)” in tobacco smokers. By contrast, “Marijuana use was associated with higher FEV1 and FVC at the low levels of exposure typical for most marijuana users. With up to 7 joint-years of lifetime exposure (e.g., 1 joint/d for 7 years or 1 joint/wk for 49 years), we found no evidence that increasing exposure to marijuana adversely affects pulmonary function.”
They conclude, “Our findings suggest that occasional use of marijuana … may not be associated with adverse consequences on pulmonary function.”
Results of the study are consistent with previous findings that reported no significant decrease in pulmonary function associated with moderate cannabis smoke exposure.
“We hypothesized that there would be a positive association between marijuana use and lung cancer, and that the association would be more positive with heavier use,” the study’s lead researcher, Dr. Donald Tashkin of the University of California at Los Angeles stated. Tashkin said he, however, did not found any association at all and even suggested of some protective effect among marijuana smokers who had lower incidences of cancer compared to non-users.
Association between marijuana exposure and pulmonary function over 20 years-Journal of the American Medical Association