A long-term study involving just over a thousand participants found that smoking cannabis regularly can alter the function of your lungs as you age. Unlike smoking a cigarette, however, cannabis appears to have a slightly different impact on a person’s breathing.
As an adult, smoking is associated with a gradual decrease in the amount of air you can expel from your lungs in a given amount of time. In comparison, smoking cannabis in the current study was linked to higher total lung volumes.
Ultimately, the authors found that both changes led to similar end results – airway constriction and hyperinflation and gas trapping.
These lung function patterns match previous results from the same cohort, which were collected 13 years earlier when the participants were 32 years old.
“Although the effects of cannabis were adverse, the pattern of changes in lung function was not the same,” says respiratory specialist Bob Hancox from the University of Otago in New Zealand.
“Research has found that prolonged cannabis use leads to excessive swelling of the lungs and increases resistance to airflow to a greater extent than tobacco.”
To date, there is little research on the lung effects of cannabis use. Some studies suggest that smoking cannabis flower can lead to acute bronchitis-like symptoms, while other studies suggest that even after seven years of smoking, lung function is not significantly impaired.
One of the main challenges is to distinguish the effects of cannabis from tobacco, since most cannabis users are also tobacco smokers.
Participants included in the current New Zealand study were no exception. Most were tobacco and cannabis smokers, but even among those who had never smoked tobacco before, the authors found similar patterns in lung function.
Although it is easy to measure the number of cigarettes a person smokes per day, there is currently no standardized form of joint. As such, the current study could only differentiate between daily cannabis smokers and those who smoke less than once a week.
This likely underestimates the amount of cannabis some participants are consuming, making it difficult to tell how much you need to smoke to put your lung health at risk.
The heaviest cannabis users in the study tended to also be tobacco smokers, further complicating the results.
“Cannabis users tend to smoke significantly fewer times per day than tobacco smokers and it is possible that participants did not smoke enough cannabis to have a measurable effect on some aspect of lung function” , note the authors.
“However, this seems unlikely given the strong associations with higher lung volumes and lower airway conductance.”
These associations were particularly strong and consistent among those who smoked both tobacco and cannabis. In fact, these participants showed a slight tendency to reduce gas transfer, meaning their lungs weren’t as efficient at exchanging oxygen for carbon dioxide.
The authors are concerned that this puts some people at risk for emphysema, although it is still unclear what these changes in lung function do to a person’s overall lung health.