Cite this article

NIDA. (2014, May 27). More Colorado drivers in fatal car crashes testing positive for marijuana. Retrieved from

press ctrl+c to copy

Science Spotlight

May 27, 2014

Emergency sign

A new NIAAA- and NIDA-funded study shows an increased number of marijuana-positive Colorado drivers involved in fatal motor vehicle crashes since Colorado’s legalization of medical marijuana in 2009.  A similar increase was not seen in the 34 states that did not have medical marijuana laws when this study was conducted.  During the same time period, there was no change in the number of alcohol-impaired drivers in fatal motor vehicle crashes in either Colorado or the 34 then non-medical marijuana states.

Although this study did not determine a cause and effect relationship between the marijuana use and the vehicle accidents, research shows that both alcohol and marijuana impair driving. The authors suggest that these findings underscore the need for enhanced education about the dangers of driving under the influence of drugs, including marijuana. For information on drugged driving, go to

For a copy of the study (published online April 23), go to

For more information, contact the NIDA press office at or 301-443-6245.