Driving with a doobie is now officially a bad idea: According to Canadian researchers, people who smoke marijuana within three hours of driving are twice as likely to cause a crash than someone who is sober.

The researchers, from Dalhousie University, examined and analyzed nine previous studies and determined that people who drove high are slightly more than twice as likely to be involved in a fatal crash. They are about 1.75 times as likely to cause a non-fatal collision.

"The impact of acute cannabis consumption on the risk of minor crashes remains unclear," according to the authors. "These results converge with those from experimental studies suggesting that cannabis impairs performance of the cognitive and motor tasks necessary for safe driving."

In 2006, more than 10 million people admitted to driving under the influence of illegal drugs; 30.5 million people admitted to driving under the influence of alcohol, according to the United States Department of Health and Human Services.

Marijuana legalization advocates say that although driving while high is more dangerous than driving while sober, it's less dangerous than driving while drunk. According to the CDC, about a third of all traffic-related deaths involve alcohol, while other drugs account for closer to 20 percent of all traffic deaths.

According to the Canadian researchers, drivers with a blood-alcohol content of .08 are about 2.7 times as likely to be involved in a car accident as a sober person.

A recent article written by NORML, an organization working to reform marijuana laws, concedes that driving high is more dangerous than driving sober, but says it is better than driving drunk.