The New York Times reports (emphasis added):
A large new government study has found that smoking marijuana on a regular basis, even over several years, does not impair lung function….
The new research is one of the most extensive looks to date at whether long-term marijuana use causes pulmonary damage, and specifically whether its impact on the lungs is as harmful as smoking cigarettes. The researchers followed more than 5,000 people over two decades and found that regularly smoking marijuana — the equivalent of up to a joint a day over seven years — did not impair performance on a lung function test….
In something of a twist, the researchers found that compared to nonsmokers, marijuana users performed slightly better on the lung function test, though the improvement was minuscule…. The finding may merely reflect marijuana smokers’ years of “training” in taking deep inhalations and holding the smoke, the researchers said.
In the near term, smoking marijuana irritates the airways and can cause coughing, and public health advocates stress that it causes impairment that reduces attention, lowers motivation and heightens the risk of accidents. Over days or weeks, chronic use can lead to problems with learning and memory….
The researchers found that for moderate marijuana smokers, an exposure of up to seven “joint years” — with one joint-year equivalent to smoking 365 joints or filled pipes, or an average of one joint a day for seven years — did not worsen pulmonary function. Dr. Kertesz noted that with heavier marijuana use, described as 10 joint-years of exposure or more, lung function did begin to decline….
Dr. Donald Tashkin, a pulmonologist at the University of California, Los Angeles, who has studied marijuana for over 30 years and was not involved in the study, said it confirmed findings from several other studies showing “that essentially there is no significant relationship between marijuana exposure and impairment in lung function.”
He said one reason marijuana smoke may not be as harmful as tobacco smoke, despite containing similar noxious ingredients, may be the fact that its active ingredient, THC, has anti-inflammatory effects.
“We don’t know for sure,” he said, “but a very reasonable possibility is that THC may actually interfere with the development of chronic obstructive pulmonary disease.”
Dr. Tashkin said he and his colleagues had found in their own research — unexpectedly — that even smoking up to three joints a day did not appear to cause a decrease in lung function.
It is, of course, obligatory for the Times to try to stick to the standard line that smoking marijuana “causes impairment that reduces attention, lowers motivation and heightens the risk of accidents”. Notice that the people who claim these things are “public health advocates” (emphasis added). Not private-sector health advocates. Not scientists. Just “public health advocates”, meaning people who tow the official government line on marijuana. People whose job it is to try to justify the government’s policy of criminalizing cannabis. Hmm…
The demonization of cannabis use by the government goes back a long time, and misinformation has always been the name of the game. Lowers motivation? Really? I’d love to see what studies support that conclusion. Sure, there are plenty of unmotivated people who smoke pot, but marijuana doesn’t make them that way. How about motivated people who like to get high and do things like exercise or something creative like playing music, painting, or writing? One could just as easily argue that cannabis use motivates people. Or just throw out this notion altogether and recognize the fact that some people who use cannabis are lazy and others are highly motivated individuals, and obviously smoking pot didn’t make them either way.
I followed the link provided where the Times says smoking can “lead to problems with learning and memory”, because I wanted to see the science behind that claim. The link is to the National Institute on Drug Abuse (NIDA), a government website. That site states:
The highest density of cannabinoid receptors are found in parts of the brain that influence pleasure, memory, thinking, concentrating, sensory and time perception, and coordinated movement.1
Not surprisingly, marijuana intoxication can cause distorted perceptions, impaired coordination, difficulty with thinking and problem solving, and problems with learning and memory. Research has shown that, in chronic users, marijuana’s adverse impact on learning and memory can last for days or weeks after the acute effects of the drug wear off.2 As a result, someone who smokes marijuana every day may be functioning at a suboptimal intellectual level all of the time.
I Googled the study cited (footnote 2), and it doesn’t support most of those assertions, only the “problems with … memory” part. The study found that heavy users “scored significantly below control subjects on recall of word lists” for up to a week after ceasing smoking. But going from an observation that users don’t do as well memorizing word lists to the conclusion that users “may be functioning at a suboptimal intellectual level all of the time” is an enormous leap of logic.
It should be emphasized that there is a difference between memorizing and learning (which is why I replaced the word “learning” with ellipses in the “problems with learning and memory” quote above). I’ve taught children for many years, and I often observe that it is the case that they try to memorize information for tests, which may get them by, but they don’t retain the information. They haven’t learned it, they just did what was necessary to pass the test without really internalizing the information. Here in Taiwan, education revolves largely around being able to spit back answers to their teachers. Understanding what is being regurgitated isn’t necessarily a requirement (and thinking critically about it, like questioning it, is not only not encouraged, but sometimes discouraged; I have frequently been told by my students, whom I teach privately, that they are often yelled at by their teachers in their public school for trying to ask too many questions).
So all this study really shows is that there is a lingering effect of marijuana use, and that one of its effects is an impaired ability to do menial tasks like memorizing word lists. The study doesn’t seem to even consider the question of why this might be—it just considers this a “deficit” and leaves it at that. But is it a “deficit”? Could it be simply that it is much harder to concentrate on boring and trivial tasks with THC in one’s system? Maybe the difference could be attributed to something like this going through the user test subjects’ heads while trying to memorize the word lists:
“Word. Word. Word. Oh, man, they want to test my memorization skills to see whether my smoking pot makes me stupider. Oh my gosh, what if it’s true?! Focus, man, you’ve got to do well on this test and prove them wrong. You’re not high right now, you can do it. Start again from the top. Word. Word. Word. Word. But, then again, they obviously want to test the lingering effects of THC on the brain, so what if I fail this test because I smoked that joint yesterday and it’s still affecting my cognitive functioning even though I’m not high right now? Shit, stop worrying about it and focus, man. From the top. Word. Word. Time! What? Crap! I didn’t even get all the way through the list!”
Does an inability to focus on pointless activities really mean that one’s “intellectual level” is “suboptimal”? Wouldn’t it depend on what task is being peformed? Why not test the subjects at something that is actually intellectually stimulating, something the subjects could get absorbed in, like doing puzzles or solving logic problems? Or, if memory is the name of the game, have them play memory (you know, the game where you flip over cards to find matching pairs)—something meaningful and stimulative, rather than trivial and boring. How would the users compare to the non-users in tasks like these?
Certainly the study supports what everybody already knows, that marijuana use causes the brain to function on a different level. But it is a subjective judgment to say it is a lower level. I would like to propose the opposite hypothesis, that the functioning is at a higher level. Or perhaps thinking of it in terms of higher and lower is altogether meaningless to begin with, since while some functions of the brain might be hindered, others might be heightened.
What if the subjects’ tasks were, rather than memorizing lists of words, something like, say, trying to identify which piece of music is played incorrectly with notes played out of pitch? Would the results show a “deficit” for cannabis users? Perhaps it would rather show a heightened ability. And if this was so, would we say people who didn’t use marijuana had a “deficit” compared to users, that they are intellectually impaired when it comes to having a good sense of relative pitch?
Getting back to the Times blog post, notice it states that according to the study “with heavier marijuana use, described as 10 joint-years of exposure or more, lung function did begin to decline”. This is extremely dishonest reporting. Actually, what the study states is
[E]xposure to marijuana (both current and lifetime) was associated with higher FVC and lifetime exposure with higher FEV1. For example, compared with zero exposure, FVC increased with greater lifetime exposure in joint-years (P = .01 for trend) and FEV1 increased with greater lifetime exposure of up to 10 joint-years and then declined to 36 mL (95% CI, −6.5 to 79) greater than the zero exposure level (P = .049 for trend).
Okay, translated, FVC is basically lung capacity (“forced vital capacity”) and FEV is the “forced expiratory volume in the first second of expiration”. So there was actually a trend discovered, as the Times correctly noted, that marijuana users tended to have increased FVC and FEV compared to non-users. The study states that “FVC increased with greater lifetime exposure”, while FEV “increased with greater lifetime exposure of up to 10 joint-years and then declined” to a level that was still “greater than the zero exposure level” (emphasis added).
Um, isn’t that pretty much the opposite of what the Times said? Doesn’t that mean that lung function is actually increased even with 10 or more “joint-years” of exposure?
The study says that while the exhale volume “became negative at very high exposure levels” of over 40 joint-years, “these negative deflections were not statistically significant”. Moreover, the lung capacity “remained significantly elevated in even heavy users”.
In sum, from the abstract (emphasis aadded):
With very heavy marijuana use, the net association with FEV1 was not significantly different from baseline, and the net association with FVC remained significantly greater than baseline.
Whoops. The Times forgot to mention these tiny details when telling readers that long-term marijuana use will cause your lung function to decline. But one shouldn’t be surprised that the Times misinformed its readers. That is, after all, largely what they do (as any regular reader of my blog will undoubtedly have picked up on by now).
And, here’s something else to consider, with regard to the eventual decline of subjects’ FEV: could it be that a person’s ability to rapidly exhale a large volume of air decreases beyond a certain age—rather than as a consequence of cannabis use? Here’s what their data shows:
Neither the Times nor the study’s authors address that question, the latter of whom may not have done so since they found the decline to be statistically insignificant.
But I have to give the Times credit. Compared to the Huffington Post, its blog post on the lung study is really good. Here’s how the HuffPo reported it (emphasis added):
Smoking a joint once a week or a bit more apparently doesn’t harm the lungs, suggests a 20-year study that bolsters evidence that marijuana doesn’t do the kind of damage tobacco does.
The results, from one of the largest and longest studies on the health effects of marijuana, are hazier for heavy users – those who smoke two or more joints daily for several years. The data suggest that using marijuana that often might cause a decline in lung function, but there weren’t enough heavy users among the 5,000 young adults in the study to draw firm conclusions.
Can you believe that? The HuffPo author (one Lindsey Tanner) and I must not be looking at the same study. Outdoing the Times for misinforming readers is really quite a feat.
Compare the Times headline, “Moderate Marijuana Use Does Not Impair Lung Function, Study Finds”, and the HuffPo headline, “Marijuana And Lungs: Study Finds Drug Doesn’t Do Same Kind Of Damage As Tobacco”, with the Natural News headline, “Cannabis smokers show greater lung capacity … than non-smokers”.
One out of those three headlines got it right as far as accurately summing up what the study actually showed.
(I replaced “and lower cancer levels” with ellipses in the Natural News headline to keep it relevant to this study only, since the study in question didn’t address the cancer issue, which you can read more about here).