Study finds pot smoking not so harmful to the lungs

by on January 11, 2012 · 4 comments

in California, Health

By Erin Allday /SFGate /  January 10, 2012

Smoking a joint or a bowl from time to time appears to cause no long-term damage to the lungs, according to a UCSF study that disproves one of the major concerns about marijuana use – that inhaling anything other than air on a regular basis must be harmful.

The study, results of which were published today in the Journal of the American Medical Association, found that the lung capacity of people who smoked marijuana was not diminished by lighting up, even among those who smoked once or twice a week.

Smoking 20 or more joints a month did have a negative impact on the pulmonary system, but that level of marijuana use is unusual. For occasional users, smoking marijuana was actually associated with a small but statistically significant increase in lung capacity – perhaps caused by the deep-breathing pot smokers use to draw the drug into their lungs.

Researchers were reluctant to give the all clear to anyone who wants to smoke pot, but 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.

 “Moderate levels of exposure to marijuana don’t seem to have any adverse effects in terms of pulmonary function,” Pletcher said. “That was a little surprising to me, honestly. I thought we were going to find a small decline in pulmonary function, similar to what we’d find with tobacco.”

 Smoking cigarettes has such dramatic, long-term health consequences – including emphysema and lung cancer – that doctors have long assumed that marijuana smoking, too, must be detrimental.

The study, which looked at 5,115 men and women over a 20-year period, found that people were just about as likely to smoke marijuana as cigarettes, and many participants smoked both. People who smoked cigarettes, however, were more likely to be heavy users – on average about eight cigarettes a day – than marijuana smokers, who lit up on average two or three times a month.

It’s likely that the main reason that marijuana smoke doesn’t seem to affect lung function the way tobacco does is because people simply don’t use the drug as much as they use tobacco. But it’s also possible, scientists said, that marijuana smoke just isn’t as damaging as tobacco smoke.

“No one would ever claim that drinking water has the same effect as drinking vodka, even though they’re both liquids and you’re ingesting them the same way. But for some reason we have assumed that because we know the negative outcomes with cigarettes, inhaling any plant material is going to have the same outcomes,” said Amanda Reiman, a UC Berkeley lecturer and director of research at the Berkeley Patients Group, a medical marijuana dispensary.

 “This study is challenging the preconceived notions we’ve had for some time about the dangers of smoking cannabis and the similarities to smoking tobacco,” she said.

{ 4 comments… read them below or add one }

elaine marie January 11, 2012 at 12:00 pm

Of course it is not as bad as cigarettes.


malcolm kyle January 12, 2012 at 6:04 am

1) Tobacco is cancer causing largely because it delivers specific carcinogens such as NNK and NNAL that are not present in cannabis. Not all “tar” is created equal, and tobacco has some of the most carcinogenic types of tar known to science, whereas cannabis does not.

2) Cannabis (marijuana) use is associated with a DECREASE in several types of cancer… potentially even providing a protective effect against tobacco and alcohol related cancer development.

Donald Tashkin, a UCLA researcher whose work is funded by NIDA, did a case-control study comparing 1,200 patients with lung, head and neck cancers to a matched group with no cancer. Even the heaviest marijuana smokers had no increased risk of cancer, and had somewhat lower cancer risk than non-smokers (tobacco smokers had a 20-fold increased lung cancer risk). Tashkin D. Marijuana Use and Lung Cancer: Results of a Case-Control Study. American Thoracic Society International Conference. May 23, 2006.

Researchers at the Kaiser-Permanente HMO, funded by NIDA, followed 65,000 patients for nearly a decade, comparing cancer rates among non-smokers, tobacco smokers, and marijuana smokers. Tobacco smokers had massively higher rates of lung cancer and other cancers. Marijuana smokers who didn’t also use tobacco had no increase in risk of tobacco-related cancers or of cancer risk overall. In fact their rates of lung and most other cancers were slightly lower than non-smokers, though the difference did not reach statistical significance. Sidney, S. et al. Marijuana Use and Cancer Incidence (California, United States). Cancer Causes and Control. Vol. 8. Sept. 1997, p. 722-728.


Jack January 12, 2012 at 11:35 am

The interesting aspect of the article was not the findings of the study; those findings have been aleady been validated by other studies over the years. The interesting aspect I found was the fact this was a federally funded study and it was still published. It does not mean the federal government will give any credence to the study, but certainly the fact it was allowed to be published is an interesting turn of position. A far cry from the federal studies released over the years which have only pandered to the governments position regarding marijuana prohibition.


Bill Ray January 12, 2012 at 5:26 pm

Yes and now that the dispensaries are all shuttered college kids now have their old jobs back. :D


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