Study: No lung danger from casual pot smoking

Add one more data point to the decades-old debate over marijuana legalization: A new study concludes that casual pot smoking - up to one joint per day - does not affect the functioning of your lungs.

The study, published in the Jan. 11 edition of Journal of the American Medical Association, also offered up a nugget that likely will surprise many: Evidence points to slight increases in lung airflow rates and increases in lung volume from occasional marijuana use.

Air flow is the amount of air someone can blow out of their lungs one second after taking the deepest breath possible. The volume measure is the total amount of air blown out once someone has taken the deepest breath possible.

Association Between Marijuana Exposure and Pulmonary Function Over 20 Years

The study of 5115 men and women took place over two decades between March 26, 1985 and August 19, 2006 in 4 American cities: Birmingham, Chicago, Oakland, Calif., and Minneapolis.

"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," according to one of the study's co-authors, Stefan Kertesz. "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."

He added that those increases, though not large, nonetheless 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," he said.

The study by researchers at the University of California, San Francisco, and the University of Alabama at Birmingham was released Tuesday by the Journal of the American Medical Association.

Echo of past findings

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. It's not clear why that is so, but it's possible that the main active ingredient in marijuana, a chemical known as THC, makes the difference. THC causes the "high" that users feel. It also helps fight inflammation and may counteract the effects of more irritating chemicals in the drug, said Dr. Donald Tashkin, a marijuana researcher and an emeritus professor of medicine at the University of California, Los Angeles. Tashkin was not involved in the new study.

Study co-author Dr. Stefan Kertesz said there are other aspects of marijuana that may help explain the results.

Unlike cigarette smokers, marijuana users tend to breathe in deeply when they inhale a joint, which some researchers think might strengthen lung tissue. But 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, said Kertesz, a drug abuse researcher and preventive medicine specialist at the Alabama university.

Roughly equal numbers of blacks and whites took part, but no other minorities. Participants were periodically asked about recent marijuana or cigarette use and had several lung function tests during the study.

Overall, about 37 percent reported at least occasional marijuana use, and most users also reported having smoked cigarettes; 17 percent of participants said they'd smoked cigarettes but not marijuana. Those results are similar to national estimates.

On average, cigarette users smoked about 9 cigarettes daily, while average marijuana use was only a joint or two a few times a month -- typical for U.S. marijuana users, Kertesz said.

The authors calculated the effects of tobacco and marijuana separately, both in people who used only one or the other, and in people who used both. They also considered other factors that could influence lung function, including air pollution in cities studied.

The analyses showed pot didn't appear to harm lung function, but cigarettes did. Cigarette smokers' test scores worsened steadily during the study. Smoking marijuana as often as one joint daily for seven years, or one joint weekly for 20 years was not linked with worse scores. Very few study participants smoked more often than that.

Like cigarette smokers, marijuana users can develop throat irritation and coughs, but the study didn't focus on those. It also didn't examine lung cancer, but other studies haven't found any definitive link between marijuana use and cancer.

[PeyoteMike420]

The fact that air flow is INCREASED is not a "surprising nugget."

[IchabodMertz]

Ahh, but what about people who vaporize marijuana? I've been vaporizing for a few years now and I must say the difference between that and regular combustion smoking is night and day. When you vaporize, you're not burning the substance into black ash, instead you throw out as much as you put in because your actually cooking the weed from green to brown and so most (of course not all) of the tar and combustible material simply does not enter your lungs. Yes, you may use up more a bit more weed than if you burned it, but I think it's well worth it!

[Kate-Shreds]

Epic Winning!

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[bobnjersey]

[A new study concludes that casual pot smoking - up to one joint per day - does not affect the functioning of your lungs.]
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one joint a day is considered 'casual'?

[timthehippie]

IKR? I know multiple 4 whom 1 joint a day is considered a 'wake up'

[GBM0106]

"It also didn't examine lung cancer, but other studies haven't found any definitive link between marijuana use and cancer." Too bad the study didn't go a little further and identify the study by Donald Tashkin at UCLA that found non-smokers having a higher incidence of lung cancer than cannabis-only smokers. Look it up.

[spaldib1]

This study is inconclusive. It tests casual use and not chronic use. How many people that smoke pot really only smoke 1-2 joints in a month? If cigarette users only smoked 1-2 cigarettes per month then studies would appear to not harm lung tissue in them as well. Chronic use is what causes the most serious harm. I know the study says they tested the use of 1 joint per day but that isn't the same equivalent of the average 9 cigarettes per day that they were comparing that to. Plus, they didn't even look into if it causes lung cancer and just ignored the throat irritation and coughing, which if chronic, could cause problems.
I don't smoke pot so I'm sure people will attack this statement and call me ignorant, but I don't feel that this study is conclusive enough to prove pot is harmless.
Plus, I feel pot should be legalized and taxed just like alcohol and tobacco. Then its use could actually contribute something to our government in the form of tax dollars. But in saying that, there would have to be standards put in place to protect those who do not want to be exposed to it, such as banning its use in public buildings/restaurants/etc

[Trail_Mix]

I agree with most of what you said, and I've smoked both for years. The article said:

"On average, cigarette users smoked about 9 cigarettes daily, while average marijuana use was only a joint or two a few times a month -- typical for U.S. marijuana users, Kertesz said."

My point is, average cigarette smoker smoke 9-10 cigarettes a day. According to this Kertesz guy, average marijuana users only smoke a few joints a month. This study is on daily use of marijuana.

Interestingly enough, while average use is a few joints a month, this study considers, "up to one joint a day," casual smoking.

I don't know if I'm really making a point, just kinda some things I found interesting.

[Snerious]

I'm pretty sure if you actually read the article you will see that they also tested people who smoked one joint a day. That seems pretty typical, sure some user smoke more but so it is with tabacco as well. The reason that they are less toxic is really because of all the crap that corporations put into tabacco. Tabacco itself would be less harmful if it were made more safely.

[joshsativa]

Wow, CBS. I'm glad to see something like this finally pop up from you, and was brought to my attention. There are a lot of great statements regarding the truth about marijuana in this article. I'd like to call attention, however, to the end of the last sentence, "other studies haven't found any definitive link between marijuana use and cancer." The fact is, other studies have found definitive link to marijuana use being the cure for many forms of cancer. It may also be good to add in your "Echos of past findings" section that it's been found in studies pot can safely replace thousands of pharmaceuticals on the market today, without having death, heart attack, or stroke on its list of possible side effects. Oh, and let's also remember to add how it was discovered that cannabis helps to prevent Alzheimer's Disease and other forms of dementia because its use stimulates brain cell growth. ;)

Thanks again for posting news I'm glad to share.

[fishhead666]

No more freedom. Its time people smell the pot burning. BIGGER GOV. MORE BIG BROTHER TELLING YOU WHAT TO DO. DONT WORRY THE NEXT THING IS THE NEW CHILD LAW COMING STRIGHT TO YOU VIA YOUR GOV. WHAT IS THIS YOU MIGHT ASK ( I DOUBT IT HOWEVER ) TWO KID PER FAMILY.....YOU KNOW THAT ONE RIGHT, CHINA LIKES IT.

B.T.W... I DONT SMOKE POT. BUT I ADVOCATE LEGALIZING DRUGS IN THIS COUNTRY. WHY? CAUSE PUTING PEOPLE IN JAIL DONT STOP DRUG ABUSE. END OF STORY.

[otamatthew]

I am dead set against legalizing marijuana. We have enough trouble with drunks on the road killing people with their irresponsible use of alcohol. We will get even more deaths with people irresponsibly using marijuana and driving under the influence. IF they can make a new variety without THC I bet it would not sell. People just want to get high.

[cstodter0127]

Where is your source in saying that there will be even more deaths if it were legalized? You really do not know the problems prohibitions cause do you?

[ForADumbComment]

You are ignorant and uninformed. There is a form of marijuana without THC. Its called HEMP! A very unique plant that can be used to make clothes, oils, and other useful by products.
Also I dont know this for sure. But I think THC is the active ingredient that is thought to help medical users. I personally use it for anxiety relief and better sleeps.

[jefe2009]

We live in a capitalistic society that thrives on energized, productive workers. That is why many corporations offer free coffee to their employees. Whereas with cannabis, the effect is one of inducing a feeling of complacency where people are quite satisfied with what they have and where they are in life - which is anathema to capitalistic productive ideals. So cannabis will continue to be demonized, as such, by employers even if it should ever be re-legalized.

[HootzMcToke]

Well that's not really the reason. its all about money. I smoke pot and i don't feel complacent, i feel energized and productive. It makes me want to do things i normally would just be "meh that's boring" I just never smoke before or during work.