(NewsNation) — Smoking marijuana can be just as damaging to the body as smoking cigarettes and may be even more harmful.

A new study suggests that marijuana smokers have higher rates of emphysema and airway inflammation than cigarette smokers.

Marijuana is the most commonly used federally illegal drug in the U.S., and 39 states have legalized some form of it.

Because of marijuana’s status as a federally illegal drug, there is less research on it than on tobacco.

One reason pot smokers may have greater damage than cigarette smokers is because cigarettes are usually filtered, while marijuana smoke is not. Marijuana smokers are also more likely to inhale more deeply than tobacco users.

There are limitations to the study, which only include 56 patients. Because of the mixed legal status of the drug, not all people are willing to admit to smoking weed and many people smoke both marijuana and tobacco. That makes it more challenging for researchers to identify the specific causes of lung damages.

Lung issues aren’t the only health problems linked to pot use. Another study found that marijuana smoke increased the risk of heart problems in rats, though researchers cautioned that they can’t draw firm conclusions about the effects on humans yet.

These studies have only focused on effects of marijuana smoke and not the health effects of ingesting marijuana in other forms, such as edibles.