Since the cold of the winter months have come upon us once again (Every year?), I have been inundated with the second-hand marijuana smoke of my neighbor. Let me try to explain. The house where I live has a forced-air central heating system through which all of the apartments are connected. I have returned to my home sanctuary on several occasions to a diaphanous zephyr of cannabis permeating everything. I don’t know what kind of clambake (Do people still use this term? I lived in Co-op houses in Ann Arbor in the late 1990s, so it may be passé now.) session he was undergoing, but the amount of smoke in my apartment was extreme. After at least four sessions of this, I left a note on his door. I do not fear confrontations, but I have found in my life experiences with people who are high (I lived in Co-op houses in Ann Arbor!) that they are not the best negotiators.
Regardless, the gaseous assaults of chemical warfare on my home and body soon stopped. But, it turns out I needn’t have worried. Apparently, according to a new study published in the Journal of the American Medical Association, marijuana smoking does not have a negative effect on lung function. Or, at least that is was the blogosphere is telling me.
What? How can this be? We have been told for years of the dangers of marijuana smoking. That it harms the lungs as tobacco does. That the only reason it isn’t quite as bad is that tobacco smokers smoke 20+ cigarettes a day, whereas marijuana smokers might light a bowl or bong a couple of times a week. This is what we have been told. Have we been lied to again?
As you might expect, the blogosphere has been buzzing with new posts. Most of the reports have titles like, “Pot Smoking Better for Your Lungs than Cigarettes: Study Finds.” But at least one, on the august New York Times Blog, has the title “Marijuana Smoking Does Not Harm Lungs, Study Finds.” Oh, dear. Please allow me to offer my expertise in reading science journals to elucidate what the report actually claims to have demonstrated and/or discovered.
The study, a twenty-year longitudinal analysis of more than 5000 study participants, focused on only two components of lung function: forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1). FVC is the volume of air that one can forcibly blow out after a full inspiration. FEV1 is the volume of air that one can forcibly blow out in one second after a full inspiration. These measures give an indication of the strength and flexibility of the lungs in conjunction with the diaphragm. They are statistics of lung function, used commonly in asthma and cystic fibrosis patients. In other words, they are something that we can measure that gives us an idea about a certain aspect of how a person’s lungs are functioning. These are two components of a field focused on the “measurement of breath” known as spirometry.
The study, however, does not claim that no lung damage occurs through the smoking of marijuana. “Prior studies of marijuana smokers have demonstrated consistent evidence of airway mucosal injury and inflammation as well as increase respiratory symptoms such as cough, phlegm production, and wheeze, similar to that seen in tobacco smokers.” Furthermore, according to the study, the results they found regarding FVC and FEV1 (no change or slight improvement) actually decrease beyond seven “joint-years” (one joint or bowl a day for seven years). That is, long-term and/or high level chronic use of marijuana does diminish the lungs’ ability to hold and expel air. This means that if you smoked pot a few times a week back in college, you do not need to worry about FVC or FEV1 (if you were worried before). If, however, you have been smoking a joint or two a day since the 1960s, you might have a reason for why it seems really hard to climb stairs or blow up your granddaughter’s party balloons.
In the end, however, there are a lot more effects of smoking marijuana than just lung elasticity. The most important ones might be in cognition, memory, ambition, and sex drive, rather than in lung damage. If you are curious, the National Institutes of Health lists many of the known effects of marijuana smoking. Personally, I enjoy my lungs, breathing, my abilities in cognition and memory, and sex. I enjoy them more than getting high. If others make a different decision, that is their business. Please, just make sure to crack a window.
Citations
Pletcher MJ, Vittinghoff E, Kalhan R, Richman J, Safford M, Sidney M, Sidney S, Lin F, Kertesz S. Association between marijuana exposure and pulmonary function over 20 years. JAMA. 2012 Jan 11; 307(2): 173-81.
The cannabis leaf image was taken from American Medical Marijuana Society website.
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