Pulmonary function in cannabis users: Support for a clinical trial of the vaporizer

Background: Debates about cannabis policy often mention respiratory symptoms as a negative consequence of use. The cannabis vaporizer, a machine that heats the plant to release cannabinoids in a mist without smoke and other respiratory irritants, appears to have the potential to minimize respiratory complaints. Methods: Twenty frequent cannabis users (uninterested in treatment) reporting at least two respiratory symptoms completed subjective ratings of respiratory symptoms and spirometry measures prior to and following 1 month's use of a cannabis vaporizer in a pre/post-design. Outcome measures included self-reported severity of nine respiratory symptoms as well as spirometry measures, including the maximum amount of air exhaled in 1 s (forced expiratory volume; FEV1) and maximum total lung volume (forced vital capacity; FVC). Results: The 12 participants who did not develop a respiratory illness during the trial significantly improved respiratory symptoms (t(11)=6.22, p=0.000065, d=3.75) and FVC, t(11)=2.90, p=0.007, d=1.75. FEV1 improved but not significantly t(11)=1.77, p=0.053, d=1.07. Conclusions: These preliminary data reveal meaningful improvements in respiratory function, suggesting that a randomized clinical trial of the cannabis vaporizer is warranted. The vaporizer has potential for the administration of medical cannabis and as a harm reduction technique. (C) 2010 Elsevier B.V. All rights reserved.