if someone were looking into the difference between cigarette smoking and marijuana smoking.
No non-smokers were included b/c the comparison was between cigarettes, which are considered a big factor in the development of bladder cancer, and those who also or only smoked cannabis.
The study compared rates of bladder cancer in the three groups - cigarette smokers only, those who smoked both, cannabis smokers only.
The cannabis smokers only had the best outcomes compared to the other two groups and those who smoked both did better than those who only smoked cigarettes.
The research aligns with prior research that notes the difference, the MAJOR difference, between inhaled cigarettes and inhaled cannabis.
Donald P. Tashkin, MD - Medical Director of the Pulmonary Function Laboratory, Professor of Medicine, University of California, Los Angeles has done the most studies related to cannabis and lung function.
He notes COPD, i.e. emphysema, is not evidenced with cannabis but it is with tobacco. loss of lung function...all lung function for the cannabis users was within the normal function in his large study. The New Zealand study confirmed this. The Arizona study found it might, in the future, lead to COPD.
COPD tends to occur later in life. This is why the study in the OP, a twenty-year study, is considered important b/c of the normal onset of COPD - or decrease in lung function.
Here's a link to a post with videos related to lung function and other health aspects from Dr. Tashkin and also Dr. David Bearman.
http://www.democraticunderground.com/101422478#post101
The Journal of the American Medical Association found that moderate cannabis smokers had BETTER lung function than those who had never smoked cannabis or tobacco.
http://pulmccm.org/2012/asthma-review/infrequent-pot-smokers-have-better-lung-function-than-non-tokers-jama/
Smoking marijuana moderately over years is strongly associated with small improvements in lung function, even compared to people who have never smoked cigarettes or marijuana, according to a study in JAMA. But the popular news media and the study authors downplayed that finding of the study, apparently to avoid sending a pro-marijuana message.
Mark Pletcher, Eric Vittiinghoff, Stefan Kertesz et al crunched numbers from the CARDIA study, which followed 5,115 young U.S. men and women for 20 years (1985-2006) collecting data on tobacco and marijuana use, and included spirometry from 20,777 clinic visits: an enormous trove of longitudinal data.
...in marijuana smokers who had smoked up to 3,650 marijuana cigarettes (10 “joint-years”), FEV1 and FVC were higher than matched nonsmokers. At these common levels of marijuana use, there was a steady dose-response relationship: the more marijuana smoked, the better the lung function (FEV1 increase of 13 mL/joint-year).
All these trends were highly statistically significant (p < 0.001), and supported by the large sample size and body of spirometric data.
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