Smoking Pot Raises Risk of Car Crashes

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In case there was any doubt in your mind that driving after smoking pot is not a good idea, a new study brings the point home: Marijuana use increases the risk of car crashes.

People who reported driving within three hours of using marijuana , or drivers who tested positive for the drug, were more than twice as likely to be involved in a car crash compared to other drivers, the study said.

The more frequently participants reported using pot, and the higher the concentration of the drug in urine, the higher their risk of a car crash.

However, the study's findings aren't exactly new. Previous studies in laboratory simulators showed marijuana use decreased driving performance. However, laboratories aren't the real world, and so the researchers said it was necessary to examine the relationship between pot use and car crashes among the general population.

The researchers reviewed nine studies published in the last 20 years, conducted in six countries. Eight of the nine studies showed pot users had a significantly increased risk of car accidents. The only study that did not find a link was a small study conducted in Thailand, where the use of marijuana is low among the general population.

The findings are important in light of the fact that marijuana is becoming more accessible due to its increased acceptability for medical use, the researchers said. In the last 14 years, 16 states and Washington, D.C., have decriminalized medical marijuana.

While the results may seem painfully obvious, the researchers said the results of their study do not prove pot use causes car crashes The study found an association, not a cause and effect link.

Other factors, including the use of multiple drugs, could affect the likelihood of car crashes, the study said. Future research should look at how the dose of marijuana, and how it's administered, affect the risk of car crashes.

"Given the ongoing epidemic of drug-impaired driving, and the increased permissibility and accessibility of marijuana for medical use in the U.S., it is urgent that we better understand the role of marijuana in causing car accidents," the researchers from Columbia University, wrote in the Oct. 4 issue of the journal Epidemiologic Reviews.

Pass it on: Marijuana use increases the risk of car accidents.

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Rachael Rettner

Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.