Study results published in October 2017 indicate that cannabis smokers were not adversely affected with “increased risk of cough, wheeze, or chronic bronchitis when compared to never-marijuana users after adjusting for covariates.”
In fact, study authors said research data indicated that “forced vital capacity” or FVC, a measurement of lung capacity, might be increased for some cannabis users due to deep breathing techniques, potentially developed while smoking cannabis.
The SPIROMICS study was published in medical journal Chronic Obstructive Pulmonary Diseases, and was conducted by a team of researchers from several U.S. universities, led by researchers from Colorado School of Public Health and funded by the National Institutes of Health (NIH). A group of 2982 subjects were divide into groups based on cannabis use status (never, former, current) and included subjects between, including former and current tobacco smokers
Noting that cannabis study findings are often controversial, authors also pointed out lack of cannabis research upon which to base standards, criteria, or comparisons. While tobacco smokers were measured in “pack years,” with numerous studies upon which to base criteria, cannabis use was measured by “joint years,” a measurement devised for the study. “One joint year is equivalent to smoking one joint or bowl, per day for one year,” the study said.
In conclusion, among other findings, study data, “revealed a lower percentage of emphysema, yet a higher total tissue volume among current and former marijuana users and a higher percentage of air trapping among former users after adjustment for covariates. Percentage of emphysema and total tissue volume are inversely related; increased inflammation could explain these associations in our population.”
“These results are likely heavily biased and should be interpreted with caution,” authors concluded. “Among older adults with a history of tobacco use, marijuana use does not appear to increase risk for adverse lung function. It is necessary to collect more epidemiologic data on marijuana exposure in a broader population to better understand its health consequences.”
The study’s publication prompted a post in the February 4th newsletter of the International Association for Cannabinoid Medicines. A summary of study findings said, “Neither current nor former cannabis use was associated with increased odds of wheeze, cough or chronic bronchitis when compared to never users. Current and former cannabis users had less emphysema and better forced expiratory volume in 1 second (FEV1%). However, heavy cannabis use was associated with more chronic bronchitis symptoms.”