WEDNESDAY, Oct. 12 (HealthDay News) -- Drivers who get behind the wheel after using marijuana run more than twice the risk of crashing compared to others, a new study finds.
The risk rises even higher if the driver has also been drinking alcohol.
The authors of a study published online Oct. 4 in Epidemiologic Reviews believe the findings are especially relevant in light of recent moves to legalize medical marijuana in many states.
"As more and more states consider medical use of marijuana, there could be health implications," said study senior author Dr. Guohua Li.
Even as alcohol use has decreased over the past four decades, illicit use of non-alcoholic drugs, such as prescription medications and marijuana, has increased, said Li, a professor of epidemiology at Columbia University Mailman School of Public Health in New York City.
A large U.S. survey in 2009 estimated that more than 10 million people aged 12 and over had driven while under the influence of illicit drugs in the previous year. And testing has revealed that 28 percent of drivers who die from a crash and more than 11 percent of drivers in general test positive for drugs other than alcohol. Marijuana is the most commonly detected drug in drivers after alcohol.
In their study, Li and his co-authors assessed information from nine prior studies in six countries looking at marijuana use and motor vehicle accidents.
The studies looked at different time frames, with some assessing marijuana use as little as one hour before driving and others looking at one year or more. According to one study cited, driving skills are acutely affected for three to four hours after use.
All but one study found a higher risk of crashes in drivers who use marijuana, and that study was a small one, conducted in Thailand, where marijuana use is relatively low.
Overall, the risk of a cras
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