In a national study, researchers at UC San Francisco found that a low to moderate level of marijuana usage is less harmful to the pulmonary system than tobacco use.

The researchers believe the data can supplement the existing knowledge regarding the beneficial aspects of low to moderate use of marijuana in treating chronic symptoms such as pain, low appetite and depression.

The authors published their findings in the Journal of the American Medical Association, stating that the relationship between long-term use of marijuana or tobacco and pulmonary function indicated marijuana was less harmful to the lungs overall. Conducted in partnership with the University of Alabama at Birmingham, the Coronary Artery Risk Development in Young Adults analyzed the effects of both tobacco and cannabis on the body’s pulmonary system. The study collected data over a 20-year period from over 5,000 healthy men and women.

While the findings suggest occasional marijuana use may not have a negative impact on pulmonary function, the study found frequent or very frequent use over a long time period still contributed to an accelerated decline in pulmonary function.

However, results were skewed by the fact that the study’s tobacco users smoked an average of 10 to 20 cigarettes per day, whereas marijuana users smoked roughly only two to three times per month, making the levels of exposure inconsistent and difficult to compare.

The study specifically measured air flow rate and lung volume of participants. The paper’s lead author Mark Pletcher, associate professor in the Division of Clinical Epidemiology at UCSF, said the researchers were surprised by the results of marijuana exposure.

Contrary to the findings for reefer, Stefan Kertesz, associate professor in preventive medicine at the University of Alabama at Birmingham, said they found the amount of tobacco smoked directly corresponded to a loss of lung volume and air flow.

However, the same results were not found with low to moderate ganja use; air flow rate actually went up with increasing levels of exposure to marijuana, to a certain point.