Marijuana use may double the risk of accidents for drivers

According to the investigators 8 of 9 studies found that drivers who use marijuana are significantly more likely to be involved in crashes than drivers who do not. Only one small case-control study conducted in Thailand, where the prevalence of marijuana use is far lower than reported elsewhere, was the exception.

Full study findings are published online in Epidemiologic Reviews.

The analysis indicates that 28% of fatally injured drivers and more than 11% of the general driver population tested positive for non-alcohol drugs, with marijuana being the most commonly detected substance.

Guohua Li, MD, DrPh, professor of Epidemiology at Columbia University's Mailman School of Public Health, and senior author points out that although this analysis provides compelling evidence for an association between marijuana use and crash risk, one should be cautious in inferring causality from these epidemiologic data alone. However, "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."

"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."

Provided by Columbia University