Minor Respiratory Complications, No Decrease In Pulmonary Function Associated With Long-Term Marijuana Smoking, Study Says

West Haven, CT: Long-term smoking of cannabis is associated with an elevated risk of respiratory complications, including an increase in cough, sputum production, and wheezing, but not a decline in pulmonary function, according to a review published in the February issue of the journal Archives of Internal Medicine.

Investigators at the Yale University School of Medicine conducted a systematic review of studies published between 1966 and 2005 that assessed the effects of marijuana smoking on pulmonary function and respiratory complications.

The data failed to show an association between long-term marijuana smoking and airflow obstruction (emphysema), as measured by airway hyperreactivity, forced expiratory volume (FEV), and other measures, investigators reported. Short-term use of cannabis was associated with bronchodilation.

Investigators did find that long-term marijuana smoking was associated with an increased risk of certain respiratory complications — including cough, bronchitis, phlegm, and wheezing. Most of these complications persisted even after researchers adjusted for tobacco smoking.

Previous reviews of long-term cannabis smoking have noted similar respiratory complications, though an association between cannabis use and lung and/or upper aerodigestive tract (UAT) cancers has not been found.

Authors suggested that cannabis inhalation via specialized delivery systems such as vaporizers would likely yield different results.

Cannabis vaporization limits users’ intake of respiratory toxins by heating cannabis to a temperature where cannabinoid vapors form (typically around 180-190 degrees Celsius), but below the point of combustion where noxious smoke and associated toxins (e.g., carcinogenic hydrocarbons) are produced (near 230 degrees Celsius). According to clinical trial data published last year in the Journal of Pharmaceutical Sciences, vaporization is a “safe and effective” cannabinoid delivery system for individuals desiring the rapid onset associated with inhalation, but who wish to avoid the respiratory risks of smoking.

“The final pulmonal uptake of THC is comparable to the smoking of cannabis, while avoiding the respiratory disadvantages of smoking,” investigators in that study reported.

For more information, please contact Paul Armentano, NORML Senior Policy Analyst, at (202) 483-5500. Full text of the study, “Effects of marijuana smoking on pulmonary functions and respiratory complications: a systemic review” appears in the current issue of the Archives of Internal Medicine.