Occasional marijuana won't harm lungs, finds study

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Researchers from University of California, San Francisco have found smoking marijuana occasionally doesn't harm the lungs. However, they also found in their study that excessive cannabis smoking does lead to lung damage.


In their study, published in the Journal of the American Medical Association, the scientists followed 5,016 men and women who were part of the Coronary Artery Risk Development in Young Adults (CARDIA) study for a period of 20 years.


Because cannabis has some of the same chemicals as cigarette tobacco, the researchers were interested in finding out if marijuana causes the type of lung damage associated with tobacco.


Fifty-four percent reported they smoked marijuana, tobacco, or both. Tobacco was smoke more often - 8 to 9 cigarettes a day compared with two or 3 episodes of marijuana use in the previous 30 days. 

The authors write:

“With up to 7 joint-years of life-time exposure (e.g., 1 joint/day for 7 years or 1 joint/week for 49 years), we found no evidence that increasing exposure to marijuana adversely affects pulmonary function.”

Measurements used to test lung damage included FEV1 - the amount of air you can blow out of your lungs in one second after taking a full, deep breath, and FVC, which is the total amount of air forcibly exhaled after taking full breath in.


In the study FVC actually improved. The researchers suggest it may be from  inhaling deeply that occurs with marijuana smoking that strengthens and stretches the lungs. 


The research team, which was led by Mark J. Pletcher, MD, MPH, notes marijuana has benefits for controlling pain, improving mood and promoting appetite. 


The finding that occasional marijuana smoking doesn't harm the lungs, might be used in support of medicinal use of cannabis to treat chronic health conditions. However, smoking pot more than 20 times a month was shown to cause a substantial decrease in FEV1 - forced exhaled (lung) volume in one-second. 


Source:

Pletcher MJ, Vittinghoff E, Kalhan R, Richman J, Safford M, Sidney S, Lin F, Kertesz S. Association between marijuana exposure and pulmonary function over 20 years. JAMA 2012; 307(2): 173-81

Marijuana use might double the chances of driving accidents

Marijuana use linked to crashes

Marijuana use linked car accidents

Research suggests if you use marijuana you may be at twice the risk of having a motor vehicle accident, compared to people who don’t use cannabis.

Researchers at Columbia University performed a meta-analysis of nine epidemiologic studies, finding people who tested positive for marijuana were twice as likely to have a car accident. The chances of a mishap while driving increased with frequency of marijuana use and concentration of the drug in the urine.

The scientists say the finding is important because of findings from a 2009 National Survey on Drug Use and Health that showed over 10 million people age 12 or older had driven under the influence of an illicit drug in the year prior to the survey.

Guohua Li, MD, DrPh, professor of Epidemiology at Columbia University's Mailman School of Public Health, and senior author says the finding should be interpreted with caution, because the research doesn’t prove cause.

Marijuana most frequently found drug linked to car crashes

Li says, “…if the crash risk associated with marijuana is confirmed by further research, this is likely to have major implications for driving safety and public policy. It also would play a critical role in informing policy on the use of medical marijuana”.

In the study, marijuana was the most frequently found drug detected following a motor vehicle accident.  More than 11% of the general driver population tested positive for non-alcohol drugs. In twenty-eight percent of fatalities, non-alcohol drugs were found in the urine or bloodstream of drivers.

In 8 out of 9 studies, the researchers found marijuana users were more like to be involved in a driving accident. Li says, “…it is urgent that we better understand the role of marijuana in causing car accidents”, that would have implications for public policy for medical marijuana. The study suggests marijuana users are twice as likely to have a driving accident, compared to non-users.

Source: Columbia University Mailman School of Public Health

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