Low to moderate use of marijuana is less harmful to the lungs than tobacco exposure, according to a new study published in the Journal of the American Medical Association. The study found that the more tobacco a person smokes, the more adversely it affects lung function. This was not true with marijuana, the researchers found.

The study included more than 5,000 adults, and followed them for more than 20 years. The researchers found people who smoked marijuana two to three times per month did not show the same reduced lung function seen in cigarette smokers, CNN reports.

“An important factor that helps explain the difference in effects from these two substances is the amount of each that is typically smoked,” researcher Mark Pletcher, MD, MPH, of the University of California, San Francisco, said in a news release. “Tobacco users typically smoke ten to 20 cigarettes/day, and some smoke much more than that. Marijuana users, on average, smoke only two to three times a month, so the typical exposure to marijuana is much lower than for tobacco.”

The researchers noted the findings suggested that very heavy marijuana use might impair lung function, but it was difficult to determine because there were so few such smokers in the study.

Marijuana smoke contains many of the same components as cigarette smoke, the article notes.