Smoking weed long-term damages lungs differently than tobacco, study says. What to know
It’s established that smoking tobacco harms the lungs and poses the risk of people developing conditions such as lung cancer — but what about weed users who’ve been blazing the plant over the years?
Long-term marijuana smoking can also damage a person’s lungs but in a way that’s different from tobacco’s effects, a recent study suggests on the “controversial” topic. Typically, it’s been assumed both substances would impair lung function similarly, according to one of the lead researchers.
“The research found that prolonged cannabis use led to over-inflated lungs and increased the resistance to airflow to a greater extent than tobacco,” study co-author and professor Bob Hancox of the University of Otago in New Zealand, said in a Feb. 3 news release.
The work comes from a study of 1,037 adult participants from Dunedin, New Zealand, that has followed their marijuana use and lung function up until age 45. Specifically, use of both cannabis and tobacco were reported at ages 18, 21, 26, 32, 38 and measured most recently at age 45, according to the study that also included researchers from Duke University in North Carolina and McMaster University in Ontario, Canada.
“I do believe that this helps us to understand the effects of marijuana on the lungs, but there is still a lot that we don’t know,” Hancox told McClatchy News. “We don’t know why marijuana appears to have different effects to tobacco.”
The research comes as college students are consuming cannabis at the highest recorded levels in decades, McClatchy News reported.
More on the findings
The researchers published earlier work based on cannabis’ effects on the lungs as a part of the long-running Dunedin study when participants were followed up at age 32. This new study is based on 13 years of follow-up data.
The entire cohort study might have “the world’s most complete data on lifetime cannabis use and lung function in a large population sample,” Hancox said in the news release.
A total 997 surviving participants were analyzed, and data was available for 881 of them, according to the study. “Associations between lung function and cannabis use were adjusted for tobacco use,” researchers wrote.
“At ages 18, 21, 26, 32, 38, and 45 years, participants were asked how many times they had used marijuana (cannabis) in the previous year.”
They measured cannabis exposure in “joint-years” from age 17. If a participant had smoked weed at least once a day for one year, that’d equal one joint-year, according to researchers.
“Tobacco exposure was calculated from the reported number of pack-years (20 cigarettes a day for one year equals one pack-year) up to 18 years, and between each assessment.”
A total 143 participants “reported using cannabis at least 6 times in the previous year at age 45,” and of these individuals, 137 declared their method of marijuana consumption.
61% said they smoked joints or cones
42% said they smoked from a pipe or bong
9% inhaled cannabis smoke through a heating method called “spots”
Others reported a combination of the smoking methods
Meanwhile, two reported they consumed cannabis orally, and another said they vaped it.
Marijuana was connected with expanded lung volume in comparison to tobacco, according to the study.
Ultimately, “both cannabis and tobacco were also associated with lower airway conductance” as well as “lower mid-expiratory airflow,” according to study authors.
“It was also found that cannabis use may also impair the ability of the lungs to extract oxygen from the breath,” Hancox explained in the news release. “This is a known consequence of smoking tobacco, but has not been demonstrated with cannabis until now.”
Study authors believe this shows the “first evidence that lifetime cannabis use may be associated with impairment of gas transfer.”
However, they acknowledge that they “only found an association between cannabis use and lower gas transfer factor among those who also smoked tobacco, although the lack of association among non-tobacco users could also be explained by their much lower exposure to cannabis.”
They note “the main difficulty in assessing the effects of cannabis on lung function is distinguishing these from tobacco.”
A limitation included how cannabis smoke exposure measurements might be “less accurate” than measuring tobacco smoke since participants could have “under-reported” their marijuana use.
But one strength included how smoking both cannabis and tobacco was assessed in each participant throughout their entire life, including an analysis of lung data since their childhood, with “a high rate of follow-up.”
What the study concludes
The study authors wrote that “there are likely to be real biological differences between the effects of cannabis and tobacco smoke, but we can only speculate about the reasons for this.”
The research also suggests cannabis smoking can be linked to bronchitis, “severe bullous lung disease in heavy” users and more, but the data is “lacking.”
“Although the findings show that smoking marijuana is not good for the lungs, we still don’t fully understand the long-term consequences for health and wellbeing,” Hancox told McClatchy News.
When asked if consuming cannabis in an edible form is better than smoking it, Hancox told McClatchy News “of course” this consumption method “would be expected to have less effect on the lungs and is likely to be better from the respiratory point of view.”
However, the professor said “I don’t know about the other effects on health and whether these are better or worse for those who eat rather than smoke cannabis.”
This story was originally published February 11, 2022 at 9:31 AM with the headline "Smoking weed long-term damages lungs differently than tobacco, study says. What to know."
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