By Steve Elliott
A report published last year in the Journal of the American Medical Association shows that — over a 20-year period — marijuana smokers generally did not experience a loss in lung function. In fact, many actually had enhanced lung capacity, which one researcher speculated might come from the practice of “deep-lunging” hits to maximize their intoxicating effects.
Whatever the cause, the fact remains that the study showed the lung function of most marijuana smokers actually improved slightly over time.
Stefan Kertesz, University of Alabama at Birmingham, who was involved in the study, said it should reassure people who smoke marijuana for medical reasons
A healthy adult man can exhale about a gallon of air in a second, according to researcher Stefan Kertesz, M.D., an assistant professor of medicine at the University of Alabama at Birmingham.
But cannabis smokers, on average, were able to blow out that gallon of air plus about 50 milliliters.
The average number of times marijuana users in the study said they smoked was two to three times per month — but even in regular users, researchers said they still saw no evidence of breathing problems.
In fact, researchers estimated that lung capacity would stay slightly larger even if a person had smoked a joint a day for seven years, or two or three joints a day for three years.
Kertesz said the study should reassure people who smoke marijuana for medical reasons.
Jeanette M. Tetrault, M.D., Yale School of Medicine: “This is a well-designed, well-described study”
[Yale School of Medicine]
”This is a well-designed, well-described study,” said Jeanette M. Tetrault, M.D., an assistant professor of medicine at Yale School of Medicine in New Haven, Connecticut.
Researchers said this “lung-stretching” property of cannabis may be due to the way people smoke marijuana — by taking and holding deep breaths with smoke — than it does with any actual benefit of marijuana itself.
The study didn’t have a lot of light to shed on heavy smokers — those who smoked the equivalent of a joint a day for 40 years, or smoked more than 25 times a month — because the number of such users in the study was small, and the scientists weren’t sure if a possible trend indicating slight lung irritation from heavy smoking was valid or not.
There is, however, another study — the largest of its kind ever conducted, in fact, by Dr. Donald Tashkin of the University of California at Los Angeles (UCLA) — which shows that marijuana smoking, even heavy, long-term smoking, does not lead to lung cancer.
Donald Tashkin, M.D., David Geffen School of Medicine, UCLA: “The main thrust of this paper has confirmed previous results that marijuana in the amounts in which it is customarily smoked does not impair lung function”
Tashkin, medical director of the pulmonary function laboratory at the David Geffen School of Medicine at UCLA, who has spent his career studying the health effects of marijuana, said the new study is helpful because it was relatively large and followed people for a long time, which gives him confidence in the results.
“The main thrust of the paper has confirmed previous results indicating that marijuana in the amounts in which it is customarily smoked does not impair lung function,” he said.
His own study of heavy, habitual marijuana smokers — people who smoked the equivalent of a joint a day for 50 years — found no harmful effect on lung function.
Tobacco’s Another Story
Tobacco smokers, on the other hand, were found to have less capacity in the amount of air they could exhale, and also in the speed at which they could empty air from the lungs. Cigarette smokers in the study saw their lung function drop steadily over the entire 20 years.
The study included more than 5,000 people in the United States. They were studied between 1986 and 2006.
“Marijuana may have beneficial effects on pain control, appetite, mood and management of other chronic symptoms,” researchers from the University of Alabama, the University of California, and Northwestern University said in a statement.
“Our findings suggest that occasional use of marijuana for these or other purposes may not be associated with adverse consequences on lung function [emphasis added],” the researchers said.
Over the 20-year period, researchers repeatedly checked two measures of lung function, reports Brenda Goodman at WebMD. One was a test that measured the amount of air forcefully exhaled in a single second; the second test measured the total amount of air exhaled after taking the deepest possible breath.
These tests help doctors diagnose chronic, irreversible breathing problems like chronic obstructive pulmonary disease (COPD).
Cigarette smoking is a leading cause of COPD; researchers expected marijuana to irritate the lungs in a similar fashion, since it contains many of the same chemicals as tobacco smoke. But crucially, the cannabinoids in marijuana smoke seem to protect the lungs and pulmonary passageways from both irritation and from cancer.
Marijuana Improves Mental Sharpness In Middle-Aged Men: Study
Not only does smoking marijuana not “burn you out,” but it’s downright good for your brain. Yet more scientific evidence — this time, that it actually appears to improve cognitive functioning among middle-aged men — comes from a 2011 medical study.
Researchers looked at a large sample of 8,992 men who “used drugs,” mostly cannabis, at age 42 and then again at age 50, reported the LA Weekly. The men were tested to measure their level of brain functioning.
Surprise, surprise — the Brits who had used illegal drugs did just as well — or slightly better! — than the chaps who had never “used drugs” at all.
When current and past drug users were lumped together as one group, their scores tended to be better than those of non-users. That advantage was small, researchers said, and might be due to the fact that people who have tried drugs tend to be better educated than those who haven’t.
“A positive association was observed between ever (past or current) illicit drug use and cognitive functioning,” the study’s authors concluded in the American Journal of Epidemiology.
Marijuana was by far the most commonly used substance among participants of the study — performed by Alex Dregan of King’s College London, reported Amy Norton at Reuters.
Dr. John Halpern,
Harvard Medical School:
“This is what you’d expect to see”
”At the population level, it does not appear that current illicit drug use is associated with impaired cognitive functioning in early middle age,” an abstract of the study concludes.
Other drugs that were asked about included amphetamines, LSD, psilocybin mushrooms, cocaine and ecstasy, but only three to eight percent of study participants said they’d ever tried those.
A small subset of participants who claimed they had been treated for their drug use — which could suggest heavy or addicted drug use, or perhaps harder drugs of choice — did not fare as well cognitively at 50, but there were so few of them, it was impossible to draw meaningful conclusions, the study’s authors said.
“In a Western population of occasional drug users, this is what you’d expect to see,” said John Halpern, a Harvard Medical School psychiatrist who has studied the potential cognitive effects of drugs.
“In some ways, this is not surprising,” Dr. Halpern said. “The brain is resilient.”
The study’s findings support the idea that the effects of marijuana and perhaps other drugs are only temporary, and that cognition isn’t damaged once the effects wear off.