Study: Occasional cannabis use does not cause lung damage

This post originally appeared in Terpenes and Testing Magazine and was republished with permission.

The relationship between cannabis and lung function has been hotly debated for decades. Many know that tobacco smoking is harmful to the lungs. If anything, the image of what a smoker’s lungs looks like is burned into the minds of many. When it comes to smoking cannabis, obvious conclusions are often drawn. Is there a scientific basis for this?

Tobacco smoking has been linked to chronic obstructive pulmonary disease (COPD). [1] It is also the leading cause of preventable death in the United States [2,3] Although cannabis smoke contains similar products of combustion, it is unclear whether cannabis destroys the lungs to the same extent.

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Some studies have shown that cannabis smoke causes inflammation of the lining of the airways and causes lung symptoms such as coughing, increased mucus production, and wheezing. [4-6] However, there are no studies that show a decrease in lung function. [7]

As the wave of legalization continues to sweep through the US, more and more people are smoking cannabis. Any long-term adverse lung effects from cannabis is a public health problem that requires immediate attention.

A study conducted by Coronary Artery Risk Development in Young Adults (CARDIA) attempted to understand both the short- and long-term effects of cannabis on lung function. [8] This was compared with data from tobacco smokers.

RELATED: Is Marijuana Smoking Bad For Your Lungs?

The study included 5,000 participants who were repeatedly exposed to tobacco and cannabis smoke. The data was collected over 20 years, with the researchers analyzing current and lifelong smoking intensity and lung function. Cannabis exposure was compared to lung function over twenty years to determine associations.

Healthy male and female adults (18-30 years of age) were included in the study. They were taken from four communities in the United States and consisted of different types of cannabis and tobacco smokers. Participants signed a declaration of consent and underwent six assessments. Pulmonary function tests were performed every 0, 2, 5, 10 and 20 years. After 20 years there was 69% retention.

RELATED: Is Vaping Cannabis Really Worse For Teenagers’ Lungs Than Vaping Tobacco?

Results: Cannabis exposure occurred at a similar rate to tobacco exposure. Tobacco exposure was linearly associated with decreased lung function over the specified time period (lower forced expiratory volume in one second (FEV1), a measure of one’s own ability to expel air; and lower forced vital capacity, FVC, the total amount of exhaled air during the FEV- Test). On the other hand, cannabis exposure had a non-linear relationship. Lower exposure to cannabis smoke resulted in increased FEV 1 and FVC. Chronic exposure decreased and in some cases reversed this effect. After 20 years of jointing (one year of jointing equals 365 smoked joints or pipe fillings (1 year * 365 days / year * 1 joint / day) lung function remained significantly higher than the baseline value. The study showed that occasional cannabis smoking was not used associated adverse effects on the lungs. [9]

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References

1- Pauwels RA, Rabe KF. Stress and clinical features of chronic obstructive pulmonary disease (COPD). Lancet. 2004; 364 (9434): 613-620. – [journal impact factor = 79.321; times cited = 956]

2- Danaei G, Ding EL, Mozaffarian D, et al. The preventable causes of death in the United States: comparative risk assessment of diet, lifestyle, and metabolic risk factors [published correction appears in PLoS Med. 2011 Jan;8(1). doi: 10.1371/annotation/0ef47acd-9dcc-4296-a897-872d182cde57]. PLoS Med. 2009; 6 (4): e1000058. [journal impact factor = 11.07; times cited = 1776]

3- Mokdad AH, Marks JS, Stroup DF, Gerberding JL. Actual Causes of Death in the United States, 2000 [published correction appears in JAMA. 2005 Jan 19;293(3):298] [published correction appears in JAMA. 2005 Jan 19;293(3):293-4]JAMA 2004, 291 (10): 1238-1245. [journal impact factor = 56.27; times cited = 4866]

4- Tashkin DP, Baldwin GC, Sarafian T, Dubinett S, Roth MD. Respiratory and immunological consequences of marijuana smoking. J. Clin. Pharmacol. 2002; 42 (S1): 71S-81S. [journal impact factor = 3.126; times cited = 167]

5- Tetrault JM, Crothers K., Moore BA, Mehra R, Concato J, Fiellin DA. Effects of smoking marijuana on lung function and respiratory complications: a systematic review. Arch Intern Med. 2007; 167 (3): 221-228. [journal impact factor = 21.87; times cited = 309]

6- Halle W, Degenhardt L. Harmful effects of non-medical cannabis use. Lancet. 2009; 374 (9698): 1383-1391. [journal impact factor = 79.321; times cited = 686]

7- Tashkin DP. Does Cannabis Use Predispose To Chronic Airway Obstruction ?. Eur Respir J. 2010; 35 (1): 3-5. [journal impact factor = 12.34; times cited = 18]

8 – MJ Pletcher, E. Vittinghoff, R. Kalhan et al. Association between marijuana exposure and lung function over 20 years. JAMA. 2012; 307 (2): 173-181. [journal impact factor = ; times cited = ]