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Objectives. To evaluate motor vehicle crash fatality rates in the first 2 states with recreational marijuana legalization and compare them with motor vehicle crash fatality rates in similar states without recreational marijuana legalization.
Methods. We used the US Fatality Analysis Reporting System to determine the annual numbers of motor vehicle crash fatalities between 2009 and 2015 in Washington, Colorado, and 8 control states. We compared year-over-year changes in motor vehicle crash fatality rates (per billion vehicle miles traveled) before and after recreational marijuana legalization with a difference-in-differences approach that controlled for underlying time trends and state-specific population, economic, and traffic characteristics.
Results. Pre-recreational marijuana legalization annual changes in motor vehicle crash fatality rates for Washington and Colorado were similar to those for the control states. Post-recreational marijuana legalization changes in motor vehicle crash fatality rates for Washington and Colorado also did not significantly differ from those for the control states (adjusted difference-in-differences coefficient=+0.2 fatalities/billion vehicle miles traveled;95% confidence interval = -0.4, +0.9).
Conclusions. Three years after recreational marijuana legalization, changes in motor vehicle crash fatality rates for Washington and Colorado were not statistically different from those in similar states without recreational marijuana legalization. Future studies over a longer time remain warranted. (Am J Public Health. 2017;107:1329-1331. doi:10.2105/AJPH.2017.303848)
A recent analysis found that medical marijuana legalization has been associated with overall reductions in motor vehicle crash fatalities, although the state-specific effects vary widely.1 Other studies of marijuana-related motor vehicle crashes before and after medical marijuana legalization have produced conflicting results.2-5 What remains unknown is whether recreational marijuana legalization affects motor vehicle crash fatality rates. The purpose of this study was to evaluate pre- and postrecreational marijuana legalization changes in motor vehicle crash fatality rates in the first 2 US states to pass recreational marijuana legalization-Washington (November 2012) and Colorado (December 2012)- and to compare them with motor vehicle crash fatality rates in 8 similar states without medical marijuana legalization or recreational marijuana legalization.
METHODS
We selected control states a priori based on their similarity to Washington or Colorado, primarily in terms of traffic and roadway characteristics but also in terms ofpopulation, drivers, vehicle ownership, and traffic laws (Appendix A, available as a supplement to the online version of this article at http://www. ajph.org). We then...