New research shows that smoking a single cannabis joint is as harmful to lungs as having up to five cigarettes in succession.
Experts at the Medical Research Institute of New Zealand found that those smoking cannabis damaged both the lungs' small fine airways, used for transporting oxygen, and the large airways, which blocked the airflow.
It means that cannabis smokers complained of wheezing, coughing, and chest tightness.
However, researchers tested just 339 people: those who only smoked cannabis, those who smoked tobacco, those who smoked both, and non-smokers.
The study found that only those who smoked tobacco suffered from the lung disease emphysema.
The research found that the extent of the damage was directly related to the number of joints smoked, with higher consumption linked to greater incapacity.
It found that the effect on the lungs of each joint was equivalent to smoking between 2.5 and five cigarettes in one go.
