Effects of smoked marijuana on lung health unknown—more research is needed

Despite the legalization of marijuana on October 17, the long-term effects of smoked cannabis on lung health are unknown and more research is needed, argue authors in a commentary in CMAJ (Canadian Medical Association Journal).

"Whereas many view marijuana as a relatively safe drug, and the numerous health benefits and safety of marijuana, especially when used for medicinal purposes, are touted in various media, others have expressed concern that the overall health benefits of 'medical' marijuana have been overstated and the drug's harms understated, as was the case for tobacco cigarettes before 1964," write Drs. Wan Tan and Don Sin, Centre for Heart Lung Innovation at the University of British Columbia and St. Paul's Hospital, Vancouver, BC.

Marijuana is quite similar to tobacco, except for tetrahydrocannabinol (THC), its active ingredient.

There is evidence of the effects of marijuana on lung health, but much of it is conflicting, with some types of research finding respiratory symptoms and increased risk of chronic bronchitis, but longer-term epidemiological and clinical studies finding less clear results.

The commentary authors call for more research into the effects of marijuana on lung health and the risk of lung cancer and chronic obstructive pulmonary disorder (COPD).

"It is essential that, with the legalization of marijuana, well-designed preclinical in vitro, animal and clinical human studies are conducted to address pressing gaps in knowledge. (...) With further research, the mysteries and myths behind marijuana can be resolved," the authors conclude.