Long-term cannabis use damages lungs, study finds

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In a new study from the University of Otago, researchers found smoking cannabis leads to lung damage, but in a different way from tobacco.

Although the effects of cannabis were detrimental, the pattern of lung function changes was not the same.

The research found that prolonged cannabis use led to over-inflated lungs and increased the resistance to airflow to a greater extent than tobacco.

It was also found that cannabis use may also impair the ability of the lungs to extract oxygen from the breath. This is a known consequence of smoking tobacco but has not been demonstrated with cannabis until now.

In the study, the team used data from the long-running Dunedin Multidisciplinary Health and Development Study.

It has documented cannabis use and measured lung function throughout adult life up to age 45 in more than 1,000 individuals born in Dunedin in 1972/73.

About 75% of the Dunedin study members had used cannabis at some time in their lives.

Respiratory doctors recognize that some patients who smoke a lot of cannabis have a distinct form of lung damage—a very severe form of emphysema that is sometimes called “bong lung”—but little is actually known about this condition.

The latest findings that heavy cannabis use leads to over-inflated lungs, increased airway resistance and impaired oxygen extraction may reflect the early signs of this disease.

The team says the latest Dunedin study findings support observations from other research that cannabis has different effects on tobacco.

The Dunedin results extend these findings with more complete measures of cannabis use and a full assessment of lung function using eleven different measures.

Why cannabis harms the lungs in different ways to tobacco is not known.

Given the widespread and increasing use of cannabis globally and the trend to decriminalization, understanding its respiratory effects is a priority.

If you care about cannabis, please read studies that high-potency cannabis may affect your memory functions, and medical cannabis can help reduce depression, improve quality of life.

For more information about lung health, please see recent studies about the stuff in the lungs that drives COVID-19 deaths, and results showing this diabetes drug could treat lung inflammation in COVID-19.

The study is published in the American Journal of Respiratory and Critical Care Medicine and was conducted by Professor Bob Hancox et al.

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