Despite all the medical benefits marijuana has, doctors and scientists have long wondered whether smoking it damages the lungs. After all, if smoking cigarettes, or basically anything else, can damage the lungs, then the smoke from marijuana should as well. But according to a recent study from Emory University, that may not be the case.
In a cross-sectional analysis using data from two rounds of the National Health and Nutrition Examination Surveys (NHANES), researchers found that adults aged 18 to 59 who smoked one marijuana cigarette — aka joint — a day were still able to forcibly exhale the same volume of air in one second (known as forced expiratory volume, or FEV1) as someone who didn’t smoke marijuana. Measuring a person’s ability to exhale is called spirometry, and it’s the go-to method for diagnosing respiratory diseases, which impair lung function.
Marijuana users who smoked joints were also more likely to report minor bronchitis-like symptoms such as cough and sore throat, Mic reported. These effects appeared less often in smokers who used vaporizers, which heat the marijuana up just enough to release the active chemicals without combusting them. That meant it probably wasn’t the marijuana that caused the symptoms, but the papers the participants used to roll their joints.
The current studies findings echo results from previous research. In one study from 2012, researchers found that people who smoked weed each day for seven years experienced no adverse effects to pulmonary function. In another study from 2013, researcher Donald P. Tashkin, from the Division of Pulmonary and Critical Care Medicine at the David Geffen School of Medicine at UCLA, found “habitual use of marijuana alone does not appear to lead to significant abnormalities in lung function when assessed either cross-sectionally or longitudinally, except for possible increases in lung volumes and modest increases in airway resistance of unclear clinical significance.”
In his 2013 study, Tashkin notes that “evidence is mixed” when it comes to the carcinogenic properties of heavy, long-term use. He also notes that heavy smoking has been linked to a reduction in the amount of tiny hairs in the bronchial tubes, called cilia, which filter the air going to the lungs, as well as a loss in the antibacterial functions of the white blood cells present on the lungs’ alveoli — the tiny tree-like balloon structures that form the boundary between the airway and the blood stream.
As with everything, moderation is key. So at least marijuana users can rest easily knowing a joint a day won’t harm their lungs in the same way tobacco smoke does.
Source: Kempker JA, Martin GS, Honig EG. Effects of Marijuana Exposure on Expiratory Airflow: A Study of Adults who Participated in the U.S. National Health and Nutrition Examination Study. Annals of the American Thoracic Society. 2014.