Inhaling marijuana associated with increased odds of developing asthma

If you're looking to reduce your chances of developing lung disease, say experts at UC San Francisco, then it may be smart to avoid inhaling cannabis.

A new study in the Journal of General Internal Medicine found that inhaling marijuana every day is associated with a 44% increased chance of developing asthma. It also increased the odds of developing chronic obstructive pulmonary disease (COPD) by 27%. 

The COPD risk may be understated, since the disease takes decades to develop, and the researchers did not have detailed information on how long people in the study had been using cannabis.

In defining the concept of inhaling, the researchers included smoking, vaping, and so-called "dabbing," which involves breathing in the vapors of concentrated marijuana. 

The study found an association between elevated risks to a person's lungs and doing any of those things with cannabis even for those who had never smoked cigarettes. 

For this group, inhaling marijuana every day was linked to a 51% increased likelihood of developing asthma. The association with COPD was also elevated, but it was not statistically significant. 

The study is the largest yet to examine the association between inhaling cannabis and risks to respiratory health among people who have not smoked cigarettes. Of the 380,000 adult participants, nearly 222,000 had never smoked tobacco. The data comes from the Behavioral Risk Factor Surveillance System, a national survey by the Centers for Disease Control and Prevention (CDC). 

Experts say the broad legalization of marijuana across much of the country and the perception that it is healthier than tobacco has led people to minimize the risks. 

The message about smoking tobacco being bad for you has gotten out there, but for cannabis, it's much less clear." 

Alison Rustagi, MD, PhD, assistant professor at UCSF and first author of the paper 

"If people are looking to reduce their likelihood of developing a chronic lung disease, they should not start using cannabis," she said. "And if they already smoke cannabis, they should do it less often."