The Washington Post “The Checkup” blog reports, “Smoking marijuana doesn’t appear to do the kind of damage to people’s lungs as smoking tobacco does,” according to a study published in the Journal of the American Medical Association. “But that may have to do more with the way marijuana is typically smoked than with anything inherent in the substance itself.”
“The paper … adds to some previous research that has also failed to find a link between low exposure … to marijuana smoke and lung damage,” the Los Angeles Times “Booster Shots” blog adds.
“Researchers led by Mark Pletcher at UC San Francisco studied 5,115 men and women in four US cities regarding their current and lifetime exposure to tobacco smoke and marijuana smoke and their lung function.”
The results revealed “that lung function declined with increased exposure to tobacco smoke” but “that same pattern was not seen with marijuana smoke.”
The AP reports, “Unlike cigarette smokers, marijuana users tend to breathe in deeply when they inhale a joint, which some researchers think might strengthen lung tissue.”
Study co-author Stefan Kertesz noted that “the common lung function tests used in the study require the same kind of deep breathing that marijuana smokers are used to, so their good test results might partly reflect lots of practice.”
He also said that “the research should not be viewed as a green light to spark up.”
ABC News reports on its website, “Measuring participants’ lung function for air flow and lung volume five times throughout the study period, the researchers found that cigarette smokers saw lung function worsen throughout the 20-year period, but marijuana smokers did not.”
However, “the heaviest pot smokers (more than 20 joints per month) showed decreased lung function throughout the study.”
According to the website of CBS News, “The findings echo results in some smaller studies that showed while marijuana contains some of the same toxic chemicals as tobacco, it does not carry the same risks for lung disease.”
Though “it’s not clear why that is so … it’s possible that the main active ingredient in marijuana, a chemical known as THC, makes the difference.”
THC “also helps fight inflammation and may counteract the effects of more irritating chemicals in the drug,” said Dr. Donald Tashkin, a doctor who was not involved in the study.
Bloomberg News reports, “The study, which followed more than 5,000 people for 20 years, is unusual in marijuana research because it involved the general population.”
Among the participants, “more than half of the people in the study reported current marijuana smoking, tobacco smoking, or both at one or more examinations.
Tobacco smokers had eight to nine cigarettes a day at the peak of their use, versus marijuana smokers reporting about two or three episodes in 30 days.”
Medscape reports the study is based on data collected for the Coronary Artery Risk Development in Young Adults (CARDIA) study, “funded by the National Heart, Lung, and Blood Institute (NHLBI),” which “is a longitudinal cohort study involving centers in Oakland, California, Birmingham, Alabama, Chicago, Illinois, and Minneapolis, Minnesota.”
The study started in “March 1985” and gathered data “on a variety of heart disease and other risk factors, including lifestyle, alcohol and drug use, diet and exercise, and behavioral and psychological variables.”
Despite these findings, “Kertesz warned that the findings shouldn’t be misinterpreted to suggest that smoking pot is good for your health: ‘It would be very incorrect to look at this study and say, ‘Wow, if I smoke marijuana, that’s going to improve my lung health,’ he told The JAMA Report,” MedPage Today reports.
In addition, “although they didn’t find any long-term breathing problems associated with occasional pot smoking, it has been linked to some short-term irritation,” WebMD explains.
Jeanette M. Tetrault, MD, an assistant professor of medicine at Yale School of Medicine who was not involved in the study, said, “The jury is still out about smoking marijuana, especially with heavy smokers and long-term chronic use. There are a lot of studies that are conflicting.”
Still, the San Francisco Chronicle says that “the results – and the fact that they were published in a major medical journal – should reassure doctors and patients who are tempted to use marijuana for treatment, primarily to ease pain and nausea, said Dr. Mark Pletcher, a UCSF epidemiologist and lead author of the study.”
Here are more of my blogs on marijuana:

• Marijuana causes brain changes similar to those in schizophrenia
• US government declares marijuana of no use medically
• Smoking pot hastens onset of mental illness
• Study says smoking marijuana may have long-lasting effects on brain development
• Teen pot use linked to psychosis
• Long-term marijuana use can double risk of psychosis in young people
• Medical Pot Ineffective as Acute Pain Treatment

• Marijuana – The Truth – Part 1
• Marijuana – The Truth – Part 2
• Marijuana – The Truth – Part 3
• Marijuana – The Truth – Part 4
• Marijuana – The Truth – Part 5
• Medical Marijuana Update #1
• Medical Marijuana Update #2
• Smoking pot hastens onset of mental illness
• Study says smoking marijuana may have long-lasting effects on brain development
• Teen pot use linked to psychosis
• Long-term marijuana use can double risk of psychosis in young people
• Medical Pot Ineffective as Acute Pain Treatment