Federal drug laws in the U.S. make it illegal to sell or possess marijuana or other forms of the plant-based drug cannabis. Despite this fact, 20 states across the country and the District of Columbia have decriminalized the medical use of marijuana (commonly known in this context as medical marijuana). In a study published in April 2014 in the journal Drug and Alcohol Dependence, researchers from two Colorado-based institutions investigated the impact that the decriminalized sale of medical marijuana has on the rate of motor vehicle fatalities involving marijuana users.
Marijuana contains an active ingredient called THC (tetrahydrocannabinol), as well as other active ingredients known collectively as cannabinoids. Together, these substances alter function in the brain by accessing sites on the brain’s nerve cells called cannabinoid receptors. Arguably, the most notable effect of this alteration is a steep increase in the level of euphoria produced inside the brain’s pleasure center. However, use of marijuana commonly triggers additional changes that include a reduced ability to perceive the passage of time, a reduced ability to interpret information coming in through the five senses, a reduced ability to think clearly or maintain focus, a reduced ability to make or recall memories and a reduced ability to properly coordinate the actions of muscles throughout the body. Either separately or in combination, several of these common effects have the potential to reduce any given individual’s capacity to exercise the skill needed to safely operate a motor vehicle.
THC and other cannabinoids contained in marijuana have known potential usefulness for the treatment of a limited number of medical conditions, including nausea in cancer patients going through chemotherapy and the profound lack of appetite found in some people with acquired immune deficiency syndrome (AIDS). In response to this fact, federal law allows doctors to prescribe standardized THC products to their patients. However, federal law does not permit the sale or use of marijuana, which can vary significantly in THC content from plant to plant. Still, in the last few years, a growing number of U.S. states have acted outside of federal guidelines (and the limits of sound scientific evidence) by decriminalizing non-standardized marijuana for a wide array of medical uses and, in some cases, establishing dispensary systems that allow private business owners to sell the drug to people who have prescriptions from their doctors.
Marijuana-Related Motor Vehicle Fatalities
In the study published in Drug and Alcohol Dependence, researchers from the University of Colorado Anschutz Medical Campus and the Denver Health and Hospital Authority used information from the National Highway Traffic Safety Administration’s Fatality Analysis Reporting System to compare the percentage of people in Colorado who were involved in fatal motor vehicle accidents while under the influence of marijuana to the percentage of marijuana-influenced people involved in such accidents in states that did not decriminalize medical marijuana. The researchers used two time frames for reference: January 1994 to June 2009 (before it became legal to sell medical marijuana in Colorado) and July 2009 to 2011. During the second period under consideration, 34 states in the U.S. had not decriminalized marijuana’s medical use.
The researchers concluded that in the two-year time period after marijuana decriminalization and establishment of a dispensary system in Colorado, the number of Coloradans who had marijuana in their systems while involved in a fatal motor vehicle accident increased by about 116 percent. In comparison, during the same time frame, the statistics for fatal, marijuana-related accidents did not go up in the 34 states that had not decriminalized medical marijuana. In addition, the rates for alcohol-related fatal crashes did not go up significantly in either Colorado or the states that didn’t decriminalize marijuana.
The authors of the study did not attempt to determine if marijuana use was the deciding factor in any fatal crashes in Colorado or in any other state. Still, they note the risks associated with operating a motor vehicle while under the influence of the drug. In addition, they note the need to improve the public’s understanding of these risks, as well as the need to improve law enforcement and public health efforts designed to prevent marijuana-influenced driving.