Marijuana users can smoke a joint a day for seven years and not damage their lungs, according to a new government study.
The study was published earlier this month in the Journal of the American Medical Association@@http://jama.ama-assn.org/@@ and financed by the National Institutes of Health@@http://www.nih.gov/@@. For 20 years, the researchers looked at the lung capacities of more than 5,000 men and women who smoked marijuana, cigarettes or both. Those who smoked one joint a day for seven years did not have lung damage, and lung capacity actually began to increase.
The study found an unexpected improvement in lung function among marijuana smokers compared to nonsmokers.
“It’s kind of surprising,” said Dr. Stefan Kertesz, associate professor at the University of Alabama at Birmingham School of Medicine and the study’s leading author@@http://well.blogs.nytimes.com/2012/01/11/marijuana-smoking-does-not-harm-lungs-study-finds/@@. “Our best guess is that (marijuana smokers) develop a skill set when they smoke marijuana.” Kertesz explained users are “trained” by taking deep breaths to hold the smoke in, but noted the increase in lung function was small.

University senior and medical marijuana advocate Sam Chapman said the study isn’t news to him.@@http://directory.uoregon.edu/telecom/directory.jsp?p=findpeople%2Ffind_results&m=student&d=person&b=name&s=Samuel+C+Chapman+@@
“It kind of just reinforces my whole perspective on marijuana use,” Chapman said, and added that he believes most students at the University don’t think marijuana is dangerous to the lungs.
Even so, marijuana contains some of the same toxic chemicals found in cigarettes, and users may experience similar health effects as tobacco smokers such as wheezing and coughing. Other short-term effects include trouble focusing, memory loss and distorted perception. It is still unclear whether marijuana can lead to long-term damage such as chronic obstructive pulmonary disease (COPD)@@http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001153/@@, a leading cause of death among Americans, especially for those who smoke cigarettes.
The study is one of the most extensive looks at the long-term health effects of the nation’s most popular illicit drug@@https://www.ncjrs.gov/htm/chapter2.htm@@. An estimated 16.7 million Americans smoke marijuana and the trend is increasing, especially among young adults.@@http://www.drugabuse.gov/publications/infofacts/marijuana@@
The National Center on Addiction and Substance Abuse at Columbia University@@http://www.casacolumbia.org/templates/Home.aspx?articleid=287&zoneid=32@@ found that from 1993 to 2005, the number of college students who used marijuana daily more than doubled@@http://doorwaysarizona.com/tag/college-students/@@.
Jennifer Summers, director of substance abuse prevention and student success at the University@@http://uonews.uoregon.edu/archive/news-release/2011/8/uo-educate-incoming-students-about-alcohol-and-substance-abuse-issues@@, doesn’t think the new study will increase marijuana use among students. She thinks high user rates are a result of the widespread availability of the drug and the lack of knowledge about the negative health effects.
Summers also noted that misconceptions of marijuana use among students contributes to high user rates. University students thought about 92 percent of the student body smoked marijuana at least once during a 30-day period, according to data from the 2010 National College Health Assessment.
“Overall, these misconceptions and misperceptions lead students to feel justified and pressured in their substance use,” Summers said. “The substance is still illegal and still has legal and health consequences that can interfere with a student’s academic success.”
Kertesz also noted that although his research shows that moderate marijuana use does not damage the lungs, it does change a person’s behavior, which may have big consequences for a student’s academic performance and career goals.