Does Marijuana Cause Lung Damage?


  • Marijuana and tobacco smoke contain similar cancer-causing compounds
  • Marijuana smoke also contains anti-cancer and anti-tumor compounds known as cannabinoids (eg. THC and CBD)
  • Studies show that regular marijuana use does not harm lung function or lead to lung cancer
  • Experts believe THC may have a protective effect on the lungs
  • Marijuana smokers are still at risk of mild conditions like chronic bronchitis – Most people are aware that tobacco use can lead to numerous lung problems, including impaired breathing and, in some cases, cancer.

While usually seen as less harmful, smoking marijuana is also thought to be bad for your lungs. But is this a myth or reality?

Marijuana Vs. Tobacco

The smoke from burning marijuana flowers contains several cancer-causing compounds, similar to those found in tobacco smoke.

Worse, cannabis smoke deposits a hefty amount of carcinogen-containing tar into the lungs – up to 4 times as much as cigarettes do, according to some studies. This is due to the way marijuana joints are usually rolled (loosely packed and unfiltered).

On the other hand, the smoke from marijuana contains a set of unique chemicals known as cannabinoids (eg. THC and CBD), which are not found in cigarette smoke. Numerous studies have found cannabinoids to have significant anti-cancer and anti-tumor effects.

This key difference is believed to play a role in the different outcomes that marijuana and tobacco have on the lungs.

What The Studies Show

Over the past decade, two large-scale studies have set out to determine the impact of heavy, sustained marijuana use on the lungs.

The first of these studies was led by Dr. Donald Tashkin – a federal researcher and lung specialist who has conducted over 20 years of research on marijuana and the lungs through generous grants from the National Institute on Drug Abuse (NIDA).

In 2006, Dr. Tashkin co-authored a study involving over 2,000 people, which found that, unlike tobacco, marijuana use did not increase the risk of lung cancer, even in individuals who reported smoking over 20,000 marijuana joints in their lifetime. On the contrary, the results seemed to show a reduction in cancer risk.

“We hypothesized that there would be a positive association between marijuana use and lung cancer, and that the association would be more positive with heavier use… What we found instead was no association at all, and even a suggestion of some protective effect.” – Dr. Tashkin

The second study was published in 2012 by a separate team of researchers from the University of California. It was the largest study ever to be conducted on marijuana smokers and involved a sample of over 5,000 adults. The researchers followed their subjects over a 20-year period and found that regular marijuana use – defined as a joint a day for 7 years or a joint a week for 20 years – had no impact on lung function.

Both studies included a sample of tobacco smokers for comparison, and both were able to confirm what we already know – cigarette smoking is directly correlated with lung cancer and impaired lung function. On the other hand, marijuana doesn’t seem to pose the same risks.

The Explanation

Although some experts have been baffled by the results of the two studies mentioned above, Dr. Tashkin points to an obvious explanation. He notes that the THC compound in marijuana may protect users against lung cancer by counteracting the effects of other cancer-causing compounds.

This theory is supported by an abundance of evidence that demonstrates the anti-tumoral and anti-cancer effects of various cannabinoids, including THC. In fact, studies involving rats have found THC to help fight tumor growth specifically in cases of lung cancer.

“The THC in marijuana has well-defined anti-tumoral effects that have been shown to inhibit the growth of a variety of cancers in animal models and tissue culture systems, thus counteracting the potentially tumorigenic effects of the procarcinogens in marijuana smoke.” – Dr. Tashkin

Other properties of THC may explain why marijuana users are not at risk of chronic obstructive pulmonary disease (COPD). COPD is a long-term lung disease that commonly affects tobacco smokers, but does not appear to occur in marijuana users.

“We don’t know for sure… but a very reasonable possibility is that THC may actually interfere with the development of chronic obstructive pulmonary disease.” – Dr. Tashkin

Risks of Marijuana Smoke

Although marijuana smokers may have little to worry about when it comes to cancer and impaired lung function, studies show that marijuana use can still lead to mild lung problems like chronic bronchitis.

Chronic bronchitis is caused by inflammation of the airway. The condition is characterized by the following symptoms:

• Persistent cough
• Extra mucus/phlegm production

Studies show that patients without noticeable impairment of lung function can still be suffering from chronic bronchitis. Unfortunately, there is no medication that can be prescribed for symptoms of chronic bronchitis caused by smoking. The best method of prevention and treatment is to simply stop smoking – even just for a temporary period of time.

Vaporizing — Is it Safer?

If you suspect you may be suffering from chronic bronchitis and stopping marijuana use is not an option, investing in a vaporizer may be your best bet. A study published in 2010 showed that marijuana smokers who switched to vaporizing experienced significant reductions in symptoms following one month of use.

Health professionals recommend vaporizers for most patients who use medical marijuana. Vaporizers allow the plant matter to be heated enough for cannabinoids to be released, but not enough to cause combustion, thereby eliminating the harmful by-products normally found in smoke.

By using a vaporizer, the risks of airway inflammation associated with marijuana smoke may be avoided.

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