Marijuana Smoking Is Associated With a Spectrum of Respiratory Disorders

A new study suggests that marijuana smoke can cause the same types of respiratory damage as tobacco smoke. Significant associations between marijuana smoking and a variety of respiratory diseases also have been confirmed by an extensive review of clinical literature

Monitoring the Effects of Tobacco and Marijuana

Dr. Brent Moore and colleagues at Yale University, the National Cancer Institute, and the University of Vermont evaluated data from a nationally representative sample of 6,728 adults. Their analysis indicated that a history of more than 100 lifetime episodes of smoking marijuana, with at least one episode in the past month, increased an individual's risk of chronic bronchitis, coughing on most days, wheezing, chest sounds without a cold, and increased phlegm.

"The most significant difference between tobacco smoke and marijuana smoke is their principal active ingredients -- nicotine in tobacco and delta-0-tetrahydrocannabinol (THC) in marijuana. Beyond that, marijuana contains at least as much tar and half again as many carcinogens as smoke from conventional tobacco," says Dr. Moore. "Quitting marijuana smoking may benefit respiratory health as much as quitting cigarettes, in addit9ion to the clear and considerable health, psychological, and social benefits of no longer abusing an illicit drug."

The researchers concluded that tobacco smokers who also smoked marijuana had a higher prevalence of most respiratory symptoms than tobacco-only smokers. Compared with tobacco-only smokers, however, those who also smoked marijuana were less likely to have had pneumonia during the previous year or to show spirometric evidence of obstructive pulmonary disorder. Commenting on this finding, Dr. Moore says that it is important to note that the marijuana smokers in the sample were significantly younger (average age 31.2 years) than the tobacco smokers (average age 41.5 years). "The marijuana related respiratory effects correspond to a relatively young population, and NHANES III did not ask participants older than age 59 about drug use," he adds. "It is likely that respiratory effects will be higher in older marijuana smokers, and, because of the high prevalence of tobacco use among marijuana smokers, there appears to be an increased risk for illness due to cumulative effects of smoking both drugs."

Marijuana's Long-Term Pulmonary Effects

Further evidence of marijuana's respiratory toxicity emerged from a study conducted by Dr. Donald Tashkin at the University of California, Los Angeles. Dr. Tashkin conducted an extensive review of clinical and epidemiological research to determine the extent to which chronic marijuana smoking might lead to long-term pulmonary effects and diseases similar to those caused by tobacco. Unlike the NHANES III data examined by Dr. Moore, the studies evaluated by Dr. Tashkin made it possible to assess a possible association between marijuana smoking and respiratory cancers.

Taken together, Dr. Tashkin's survey of clinical and epidemiological studies and Dr. Moore's assessment of self-reported and clinically observed effects provide an extensive catalog of respiratory and pulmonary damaged associated with marijuana smoking. Smokers are subject to:

Coughing and phlegm production on most days;
Wheezing and other chest sounds;
Acute and chronic ronchitis;
Injury to airway tissue, including edema (swelling), increased vascularity, and increased mucus secretion; and
Impaired function of immune system components (alveolar macrophages) in the lungs.

Moore, B.A., et al. Respiratory effects of marijuana and tobacco use in a U.S. sample. Journal of General Internal Medicine 20(1):33-37, 2005.

Tashkin, D.P. Smoked marijuana as a cause of lung injury. Monaldi Archives for Chest Disease 63(2):93-100, 2005.

Hashibe, M., et al. Marijuana use and aerodigestive tract cancers: a population-based case control study. Cancer Epidemiology, Biomarkers & Prevention (In Press).