According to a new study, cannabis legalization – whether for medical or recreational purposes – is NOT associated with an increase in traffic accidents or fatalities.
Kansas State University graduate student Andrew Young analyzed traffic fatality data over a 23-year period using two different models to determine the impact of cannabis laws on driving accidents. He first conducted a regression analysis, which is a set of statistical processes used for estimating the relationships among two or more variables. This showed no evidence of an increase or decrease in traffic fatalities following cannabis legalization.
After that, Young used a difference-in-differences model where he compared the average change over time in the outcome variable for the treatment group vs a control group, or in this case, legal states vs control states. He looked at an eight-year period starting five years before the state in question legalized cannabis.
“Legalizing marijuana is not found to be a statistically significant predictor of fatality rates,” Young concluded. “This finding means that the legalization of marijuana for both medical and recreational purposes is not associated with either a reduction or increase in fatalities per 100,000 vehicle miles traveled.”
In Arizona, for example, medical cannabis has been legal for years and traffic fatalities there are on par with Wyoming and South Dakota, where cannabis is strictly prohibited. On the other hand, Colorado, a legal state, had more fatalities than Georgia and Iowa at one point, but this uptick began years before cannabis was legalized and it leveled out around 2013. In Washington D.C., traffic fatalities actually dropped after cannabis was legalized and they remain lower than Utah and Virginia, both of which are illegal cannabis states.
“The results of the analysis suggest that there is no statistically [significant] relationship between marijuana legalization and fatal crashes,” Young wrote. “These findings suggest that concerns of policy makers and the public that legalizing marijuana will worsen road safety are not entirely founded. According to the difference-in-differences model, the recent upward trend of traffic fatality rates nationwide is not a result of medical marijuana legalization. In fact, the legalization of marijuana is not found to be a predictor of traffic fatalities.”
This isn’t the first study to debunk the idea that cannabis legalization leads to an increase in car accidents and subsequent fatalities. This research mirrors the results of a significant study published in the American Journal of Public Health in 2017.