The rate of fatal car crashes did not significantly increase in the first three years after recreational marijuana was legalized in Washington and Colorado, according to a new study published this week in the American Journal of Public Health.
The researchers from the University of Texas at Austin drew on statistics of annual statewide motor vehicle crash fatalities. They used statistical analysis to compare motor vehicle crash fatalities between 2009 and 2015 in Washington, Colorado (these two states legalized recreational marijuana in 2012), and eight control states. Alabama, Indiana, Kentucky, Missouri, South Carolina, Tennessee, Texas, and Wisconsin were chosen as the control states since they all have comparable traffic, roadway, and population characteristics, yet do not have recreational marijuana legalization.
Overall, annual motor vehicle crash fatality rates decreased over this six-year period, from 12.8 fatalities per billion vehicle miles traveled in 2009 to 11.4 fatalities per billion vehicle miles traveled in 2015. Washington and Colorado witnessed a 0.1 fatalities per billion vehicle increase in the years after recreational marijuana was legalized. Using difference-in-differences analysis, they concluded these post-legalization rates were not significantly different from those observed in the states where recreational marijuana is still illegal.
“We found no significant association between recreational marijuana legalization in Washington and Colorado and subsequent changes in motor vehicle fatality rates in the first three years after recreational marijuana legalization,” the researchers concluded.
Of course, regardless of their findings, driving under the influence of marijuana is not a good idea. As previous studies have shown, there is evidence of a direct relationship between blood THC (the primary psychoactive component of marijuana concentration) and impaired driving ability.
The debate about recreational and medicinal marijuana continues to rage on, while constantly throwing up a lot of seemingly contradictory statistics. For example, these findings go against a similar (and more widely-publicized) study that came out this week by the Highway Loss Data Institute (HLDI). This car insurance research organization found collision insurance claims are “about 3 percent higher overall than would have been expected without legalization.” Another study last year, also found fatal road accidents involving stoned drivers had doubled, from 8 to 17 percent, between 2013 and 2014, after Washington legalized marijuana.
A lot of factors can explain these differences, whether it is simply different data or an ideology guiding the interpretation of facts. Simply put, since there is currently just a few years' worth of statistics available on the matter, there's not enough evidence to draw hard conclusions yet. Until then, the issue is bound to remain hazy and ripe for debate.