Using marijuana carries legal risks, but a new study shows that the consequences of occasionally lighting up do not include long-term loss of lung function, according to a new study by University of Alabama at Birmingham researchers published in the January 11, 2012, issue of the Journal of the American Medical Association.
Marijuana is the most commonly used illicit drug in the United States, according to the National Survey on Drug Use and Health. In 2009, 16.7 million Americans ages 12 and older reported using marijuana at least once in the month prior to being surveyed. In addition, since 1996, 16 states and Washington, D.C., have legalized the medical use of marijuana to help manage the symptoms of many diseases, including cancer, AIDS and glaucoma.
“With marijuana use increasing and large numbers of people who have been and continue to be exposed, knowing whether it causes lasting damage to lung function is important for public-health messaging and medical use of marijuana,” says the study’s senior author, Stefan Kertesz, M.D., associate professor in the UAB Division of Preventive Medicine and with the Center for Surgical, Medical and Acute Care Research and Transitions at the Veterans Affairs Medical Center in Birmingham.
Kertesz says it’s long been known that marijuana smoke has many irritant chemicals found in tobacco smoke and can cause lung irritation, wheezing and cough immediately after use; however, the research on long-term effects on lung function have inconsistencies.
Using a large national database, the research team compared the lung function of marijuana and tobacco smokers during a 20-year period. The data revealed that tobacco smoke had exactly the effect shown in all prior studies — increasing a person’s cumulative exposure to cigarettes results in loss of air flow and lung volumes; the opposite was true for marijuana smoke.
“At levels of marijuana exposure commonly seen in Americans, occasional marijuana use was associated with increases in lung air flow rates and increases in lung capacity,” Kertesz says. “Those increases were not large, but they were statistically significant. And the data showed that even up to moderately high-use levels — one joint a day for seven years — there is no evidence of decreased air-flow rates or lung volumes.”