Regularly inhaling cannabis increases risk of asthma, according to largest study of its kind

A woman smokes cannabis in a Toronto park. THE CANADIAN PRESS/Chris Young

New research suggests smoking or vaping cannabis products regularly may put users at a greater risk of developing asthma.

The study by University of California, San Francisco connected the inhalation of cannabis on a daily basis with a 44 per cent increase in the chance of developing asthma.

Researchers said in a news release Friday that inhaling marijuana every day also amplified the risk of developing obstructive pulmonary disease (COPD) by 27 per cent. In fact, that risk may be understated, they said, since it takes the condition decades to develop and researchers didn’t have detailed information around how long study participants had been using the drug.

For the purposes of this research, “inhaling” covered various methods of cannabis use, including smoking, vaping and dabbing, which involves breathing in vapours from a concentrated form of cannabis.

The study, published in the Journal of General Internal Medicine, also found a link between higher risks to a person’s lungs and inhaling cannabis, even for those who had never smoked cigarettes, researchers said. It is the largest study of its kind, involving 380,000 American adults, nearly 222,000 of whom had never smoked tobacco.

For those who’d never smoked tobacco, only cannabis, inhaling cannabis daily was linked to a 51 per cent increased likelihood of developing asthma, researchers said. While the link with COPD was also increased, it was not statistically significant.

The legalization of cannabis and the notion that it’s “healthier” than tobacco has led people to downplay its risks, according to experts.

“The message about smoking tobacco being bad for you has gotten out there, but for cannabis, it’s much less clear,” said Alison Rustagi, an assistant professor at UCSF and first author of the paper, in a news release. “If people are looking to reduce their likelihood of developing a chronic lung disease, they should not start using cannabis.”

She said people who already smoke cannabis and are concerned about the risks should consider smoking less.