Marijuana use may double the risk of accidents for drivers
Over 10 million people age 12 or older are estimated to have driven under the influence of illicit drugs in the prior year, according to a 2009 National Survey on Drug Use and Health. While marijuana is the most commonly detected non-alcohol drug in drivers, its role in causing crashes has remained in question. To examine the link between marijuana use by drivers and risk of a car accident, researchers at Columbia University did a meta-analysis of nine epidemiologic studies and found that drivers who test positive for marijuana or report driving within three hours of marijuana use are more than twice as likely as other drivers to be involved in motor vehicle crashes. The researchers also found evidence that crash risk increases with the concentration of marijuana-produced compounds in the urine and the frequency of self-reported marijuana use.