Smoking a joint from time to time won’t damage the lungs, even after years of drug use, according to a study led by UCSF researchers that disproves one of the major concerns about marijuana – that smoking it must be just as risky as lighting up a cigarette.
The study, results of which were published Tuesday in the Journal of the American Medical Association, found that the lung capacity of people who smoked marijuana was not diminished by regular toking, even among those who smoked once or twice a week.
Only heavy marijuana users – those who smoked 20 or more joints a month – saw a negative impact on the pulmonary system, but that level of marijuana use is unusual, researchers said. In fact, they said, it may be that marijuana smoke doesn’t affect lung function the way tobacco does simply because people don’t smoke as many joints as they do cigarettes.
The results should reassure doctors and patients who are considering using marijuana for medical care, primarily to ease pain and nausea, said Dr. Mark Pletcher, a UCSF epidemiologist and lead author of the study.
But that’s not to say that Pletcher or his colleagues are ready to give the all clear to anyone who wants to smoke pot.
‘Issue with Marijuana’
“This study shouldn’t be interpreted as marijuana is totally harmless,” said Dr. Stephen Sidney, a study author with Kaiser Northern California’s division of research in Oakland. “We don’t see marijuana having a big impact on lung function or lung disease. But it doesn’t mitigate the fact that we have an issue with marijuana, at least in terms of dependence on it.”
Smoking cigarettes has such dramatic, long-term health consequences – including emphysema and lung cancer – that doctors have long assumed that marijuana smoking, too, must be detrimental.
Heavy marijuana use may indeed turn out to be just as risky as cigarette smoking, but that will be tough to prove because so few people smoke as much pot as they do tobacco. And not all scientists are convinced that marijuana smoke is actually as deadly as cigarette smoke.
“No one would ever claim that drinking water has the same effect as drinking vodka, even though they’re both liquids and you’re ingesting them the same way,” said Amanda Reiman, a UC Berkeley lecturer and director of research at the Berkeley Patients Group, a medical marijuana dispensary. “But for some reason we have assumed that because we know the negative outcomes with cigarettes, inhaling any plant material is going to have the same outcomes.
“This study is challenging the preconceived notions we’ve had for some time about the dangers of smoking cannabis and the similarities to smoking tobacco,” she said.
For occasional users, smoking marijuana was actually associated with a small but statistically significant increase in lung capacity, according to the UCSF study. That increase wouldn’t be noticeable to the individual – and certainly shouldn’t be interpreted as a beneficial effect of smoking marijuana, scientists added – but it may be related to the deep breathing pot smokers use to draw the drug into their lungs.
The study looked at 5,115 men and women over a 20-year period, starting in 1985, who were part of a national clinical trial meant to look at heart disease risk in young adults. The smoking researchers used data collected on tobacco and marijuana use, along with regular tests of pulmonary function.
Pot and cigarettes
Study participants were just about as likely to smoke marijuana as cigarettes, and many participants smoked both. People who smoked cigarettes, however, were more likely to be heavy users – on average about eight cigarettes a day – than marijuana smokers, who lit up on average two or three times a month. The study lumped together all types of inhaled marijuana use, meaning researchers did not differentiate among those who smoked joints or pipes or any other implement.
The researchers noted that while most marijuana smokers may not experience long-term lung problems, they may still suffer from coughs and other temporary, relatively minor irritations to the throat and lungs.
Dr. Stephen Ruoss, a Stanford pulmonologist who was not involved with the study, was quick to note that while the results may show that smoking pot isn’t terrible for the lungs, that’s hardly a robust endorsement for getting stoned.
“If you inhale the smoke of a combustible organic material – either tobacco leaf or marijuana leaf – is that a good thing for your lungs? The safe answer is no,” Ruoss said. “The hunch is that the more you smoke, the greater the detrimental effect on your lung function. Even with marijuana.”
Longtime pot smoker
But Oakland resident La Wanda Martin, 44, said she’s always assumed that smoking marijuana was safer than smoking tobacco. She’s been smoking pot for more than 30 years, in part to treat back pain and anxiety. She is currently lighting up several joints a day, which she buys from Oaksterdam University, a cannabis industry training school.
“Cigarettes are worse to use,” Martin said. “When you buy from a cannabis club, you know what you’re getting. I don’t know what they put in those cigarettes.”
Source: San Francisco Chronicle (CA)
Author: Erin Allday, Chronicle Staff Writer
Published: Wednesday, January 11, 2012
Copyright: 2012 San Francisco Chronicle