Cannabis or tobacco, which is more harmful to the lungs?

By João R. Negromonte

It is not new that we know the risks of adult use – when combustion of the components occurs – of both tobacco and cannabis. However, scientists have discovered that there are slight differences in how each one affects a person's breathing.

The study that brought together researchers from New Zealand, the USA, and Canada, published in the American Journal of Respiratory and Critical Care Medicine, showed that the consumption of tobacco and cannabis increases hyperinflation (air trapping in the lungs); however, there is evidence of increased resistance in the large airways and lower average expiratory airflow in cannabis users.  

But what does this mean?  

According to the co-author of the study, Professor Bob Hancox: “Although the effects of cannabis have been harmful, the pattern of changes in lung function was not the same. Furthermore, prolonged cannabis use led to overly inflated lungs and increased resistance to airflow to a greater extent than tobacco,” reveals the researcher, who also highlights:

"We think that both substances can impair the lungs' ability to extract oxygen from breathing. However, this is a known consequence of smoking tobacco, but it has not been demonstrated with cannabis until now.”

Methodology

The research was conducted through data collection from 1,000 adult individuals who regularly used cannabis. Born in Dunedin, New Zealand, between 1972 and 1973, the study followed these patients throughout their lives, observing factors such as their total lung capacity, functional residual capacity, residual volume, and alveolar volume, along with lower average expiratory flows, airway conductance, and air transfer factor.

The information revealed that even after quitting frequent cannabis use, the majority of study participants, 88%, showed no changes in spirometry (pulmonary function test). 

For Hancox, there is still little research revealing the real effects of cannabis on the lungs. This occurs, according to the researcher, because in many parts of the world, cannabis is still an illegal plant, which makes access difficult.

“Although cannabis is one of the most consumed substances in the world, there are still few studies on its real effects in the short, medium, and long term, thus making accurate diagnosis difficult.”

“It is clear that people who smoke cannabis and tobacco will likely suffer lung damage from both substances, but given the widespread and growing use of cannabis worldwide and the trend towards decriminalization, understanding its respiratory effects is a priority,” concludes Professor Hancox.