'

The study was a 2nd study. The first study lasted 15 years.....

Cannabis Therapeutics in HIV/AIDS - Google Book Search


There have been several studies on marijuana and lung function, but the data is conflicting, as can be seen by actually researching the topic.

However, studies have yet to show that marijuana actually increases overall lung cancer mortality. This is probably because many marijuana users also smoke cigarettes, and many marijuana users smoked for a period in their youths then quit. Similarly, marijuana smokers are considered at increased for chronic obstructive pulmonary disease, although no documented cases specifically linking marijuana with COPD have been found. Heavy marijuana smokers, who consume three to four marijuana cigarettes daily, experience the same cough, wheezing and sputum production of a pack-a-day smoker.

Finally, marijuana is known to increase the heart rate (e.g., tachycardia). This may worsen underlying heart disease or aggravate existing high blood pressure. One study has shown that the risk of suffering a heart attack increases almost five times in the hour after smoking marijuana. People with existing heart disease are strongly encouraged to avoid marijuana.

Illegal Drugs & the Heart

Cannabis and Cannabinoids ... - Google Book Search

The Institute of Medicine concluded in its Mar. 1999 report titled "Marijuana and Medicine: Assessing the Science Base":

"A number of animal studies have revealed respiratory tract changes and diseases assoicated with marijuana smoking, but others have not. Extensive damage to the smaller airways, which are the major site of chronic obstructive pulmonary disease (COPD), and acute and chronic pneumonia have been observed in various species exposed to different doses of marijuana smoke. In contrast, rats exposed to increasing doses of marijuana smoke for one year did not show any signs of COPD, whereas rats exposed to tobacco did."

Can marijuana help people with asthma or other breathing disorders?

The evidence concerning a possible link between cannabis smoking and COPD has not yet been conclusively established. A number of studies indicate a causal relationship between the two, whereas others contradict these findings[xii]

British Lung Foundation | Lung stats and facts | Cannabis

While one day it may be proven that marijuana smoking can cause COPD, that day is not today.