January 12, 2017 3 min read

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A new study from Columbia University found that traffic fatalities have fallen in seven states where medicinal cannabis is legal and that, overall, states where medical marijuana is legal have lower traffic fatality rates than states were medical marijuna remains illegal.

The study found that “medical marijuana laws were associated with immediate reductions in traffic fatalities in those aged 15 to 24 and 25 to 44 years, and with additional yearly gradual reductions in those aged 25 to 44 years.” Medical marijuana is now legal in 28 states.

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Study details

Seven researchers from Columbia’s Mailman School of Public Health worked on the study, with two more researchers from the University of California at Davis and Boston University. They published the study in the American Journal of Public Health.

The researchers used traffic accident data from 1985 to 2014, about 1.2 million accidents. They focused on the relationship between medical marijuana laws and the number of fatal traffic accidents, examining each state with legalized medical marijuana separately.

They also looked at the relationship between the existence of medical marijuana dispensaries and traffic accidents, finding a reduction in the number of fatal accidents among those ages 25 to 44 in areas where dispensaries were open.

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Report conclusions

The researchers concluded that both medical marijuana legalization and dispensaries were, on average, associated with a reduction in traffic fatalities, particularly among drivers 25 to 44-years-old.

They suggested a few possibilities for this conclusion.

Those under the influence of marijuana are more aware of their impaired condition than those under the influence of alcohol and may more often make the choice not to drive.

More people have replaced going out to drink in bars with partaking of marijuana at home, reducing the number of impaired drivers on the road.

An increased police presence in areas where medical marijuana is legal could have led to fewer people attempting to drive while under the influence of marijuana.

“Instead of seeing an increase in fatalities, we saw a reduction, which was totally unexpected,” Julian Santaella-Tenorio, the lead researcher on the study, told Reuters.

Findings varied by state. Rhode Island and Connecticut saw increases in traffic fatalities after medical marijuana became legal. California and New Mexico saw double-digit drops immediately after legalization, followed by increases.

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The varying statistics point to the need for further study into each state’s laws and how they have been implemented, Santaella-Tenorio said.

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