When it comes to the destruction of lung tissue, smoking one joint of marijuana may cause about the same amount of harm as smoking one pack of cigarettes. This is the conclusion of the leading Swiss thorax surgeon Ralph Alexander Schmid after having seen seventeen young patients at the University Hospital Insel in Berne. He and his team just have published their findings on emphysema and secondary pneumothorax in young adults smoking cannabis.
Emphysema is the destruction of the small air sacs, the alveoles, in lung tissue: Their walls disappear and they conflate into ever bigger air sacs. Schmid has seen air sacs up to ten centimeters (four inches) in diameter in the upper part of the lungs, see photo.
Such a damage has never been found before in so young people, between nineteen and forty-three years of age. Rather it is typical for heavy smokers, sixty or more years of age, who have been smoking four or more packs of cigarettes a day for many years. It is this comparison of damage that brings Schmid to the conclusion that one joint of marijuana equals one pack of cigarettes in causing emphysema. The young people in Schmid's study have smoked up to eight cannabis joints a day.
In New Zealand, Sarah Aldington and co-workers have done a similar study on the effects of cannabis on lung functions. According to their estimate, one joint equals three to six cigarettes in its effect on lung function. Emphysema have not been typical in the NZ study where smokers of more than five joint-years have been included - a joint-year is one joint per day for a year. In the Swiss study, the young smokers have consumed thirty or more joint-years. This dose difference most likely explains the discordant findings of the two studies.
Take-away: Cannabis harms the lung; one joint equals five cigarettes up to one pack, depending on the type of harm and on the intensity and duration of exposure.
Photo credit: Swiss TV, Puls