Marijuana is the most commonly used illegal drug in the U.S. and is often used for medical purposes.
Researchers at the University of Alabama at Birmingham wanted to know if it caused any long-term lung damage.
After studying a national database, they found occasional marijuana use improves lung air flow rates and lung capacity.
However, the evidence wasn't strong enough to recommend marijuana as a treatment for better lung health.
Experts also say using marijuana increases the risk for heart attack and can impair the immune system.
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