Here’s a great study for those of us who grew up in the 60’s, 760’s or, for that matte, up till present time. Smoking marijuana may not be as bad for our lungs as our parents, doctors (or we, to our kids) have said. A study published in the January 11, 2011 issue of JAMA titled “Association between Marijuana Exposure and Pulmonary Function over 20 Years” has come to the conclusion that…well before I give away the punch line let me set up the story (I mean the study).

There has been an ongoing survey in which, among other health issues, the pulmonary function of young adults has been followed for 20 years. It’s called The Coronary Artery Risk Development in Young Adults (CARDIA). The study was designed to measure risk factors for coronary disease (hence the title) in a total of 5115 men and women aged 18 through 30 over a period of 20 years in four U.S.A. communities (Oakland, Chicago, Minneapolis and Birmingham). The participants were felt to comprise a broad cross-section of typical tobacco and marijuana use patterns. They underwent a baseline examination with 6 follow-up exams over a total of 20 years. Pulmonary function testing was performed in years 0, 2, 5, 10 and 20. At each visit the use of tobacco (cigarettes smoked a day) and intensity of marijuana use (episodes in the last 30 days) was assessed. For the latter there was a questionnaire that asked about number of joints or pipe bowls smoked per episode. (No, they did not ask about brownies). This was then put in scientific terms or “joint years”. One joint a day or 365 joints a year was equal to 365 filled and smoked pipe bowls and this was termed a one-joint year. (Some would simply say it was a good year…I’m having a blast this!)

Here are the results: More than half of the participants (actually 54%) reported current marijuana smoking, tobacco smoking, or both on one or more exams. The tobacco smokers tended to have a lower education and income and to be slightly shorter and less active, whereas marijuana smokers tended to be taller and more active. (I’m not sure what to do with this fact.). To no one’s surprise, tobacco smoking (both current and lifetime) was associated with a decrease in pulmonary function. BUT, exposure to marijuana was NOT, and was actually associated with improved function! (This was measured with volume of forced expiration and something called forced vital capacity, which basically measures the ability of the lungs to expand, take in and let out air). But there was a caveat…. too much smoking of marijuana leveled this benefit or even reversed it.

The authors calculated that with 7 joint-years of lifetime exposure (which equals 1 joint a day for 7 days or 1 joint a week for 49 years) there was no evidence that marijuana adversely affected pulmonary function. Higher levels were not deemed equally safe, but the authors admitted that they had insufficient numbers of heavy users to confirm this.

Now why, one would ask, does smoking marijuana increase pulmonary function? (At least that was one of my questions.) Well, l some investigators have proposed that the deep breaths that are taken to get the marijuana smoke into the lungs (those reading this will probably know what I mean) can stretch the lungs and allow them to take in a larger volume of air. Also the musculature of the chest may improve…..a sort of “aspiratory training”.

The authors state at the end of the article: “Marijuana may have beneficial effects on pain control, appetite, mood and management of other chronic symptoms. Our findings suggest that occasional use of marijuana for these or other purposes (and I am assuming they mean recreation) may not be associated with adverse consequences on pulmonary function. It is more difficult to estimate the potential effects of regular heavy use….; however our findings do suggest an accelerated decline in pulmonary function with heavy use and a resulting need for caution and moderation when marijuana use is considered”

I wonder how many rewrites and consultations with lawyers were needed to come up with that last published sentence. In any case, occasional use doesn’t seem to hurt the lungs. I know a lot of people who will be reassured by this. I can actually tell them to “put this in their pipe and smoke it” (Purely a common expression and not meant to actually encourage marijuana use.) Amazing that smoking tobacco remains perfectly legal…