Effect of cannabis smoking on lung function and respiratory symptoms: a structured literature review.

As cannabis use increases, physicians need to be familiar with the effects of both cannabis and tobacco on the lungs. However, there have been very few long-term studies of cannabis smoking, mostly due to legality issues and the confounding effects of tobacco. It was previously thought that cannabis and tobacco had similar long-term effects as both cause chronic bronchitis. However, recent large studies have shown that, instead of reducing forced expiratory volume in 1 s and forced vital capacity (FVC), marijuana smoking is associated with increased FVC. The cause of this is unclear, but acute bronchodilator and anti-inflammatory effects of cannabis may be relevant. Bullous lung disease, barotrauma and cannabis smoking have been recognised in case reports and small series. More work is needed to address the effects of cannabis on lung function, imaging and histological changes.