U.S.-Canadian researchers say car crash deaths involving cannabis on the rise in the U.S.

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Research out of the Boston Medical Center, Boston University and the University of Victoria indicates people who died in motor vehicle collisions (MVC) involving cannabis had 50 per cent greater odds of also having alcohol in their system.

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Published online last week in the American Journal of Public Health, investigators came to their findings after exploring 19 years of data from the Fatality Analysis Reporting System, which covers fatal crashes on public roads from 2000 to 2018.

“Trends in fatalities involving alcohol have remained stable,” study authors write.

But with regard to cannabis, the percentage of fatalities involving cannabis increased from nine per cent in 2000 to 21.5 per cent in 2018, while those involving cannabis and alcohol jumped from 4.8 per cent in 2000 to 10.3 per cent in 2018, the findings indicate.

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“These results suggest that as (U.S.) states have loosened cannabis policies, cannabis and alcohol have increasingly been used together when driving,” notes a statement from the Boston Medical Center. An additional concern is what appears to be little attention being paid to “the connection between alcohol and cannabis use,” the statement reports.

“There has been progress in reducing deaths from alcohol-impaired driving, but our study suggests that cannabis involvement might be undercutting these public health efforts,” argues senior author Dr. Timothy Naimi, an adjunct professor at Boston University Schools of Medicine and Public Health, and director of the Canadian Institute of Substance Use Research in Victoria.

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As it stands in the U.S., almost 40 per cent of crash deaths involve alcohol and 30 per cent involve alcohol above the legal limit for driving.

But cannabis was found to be “a risk factor for alcohol co-involvement, even at levels below the legal limit,” researchers note.

“These results also show that cannabis-involved car crashes are more likely to involve the deaths of passengers as well as individuals younger than 35 compared to crash deaths not involving cannabis,” they add.

Lead author Marlene Lira, an epidemiologist at Boston Medical Center, acknowledges people can test positive for cannabis weeks after consumption. “However, we can say that fatalities from crashes involving cannabis are more likely to have also involved alcohol, even if we don’t know the exact level of cannabis,” Lira says.

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Australian research suggests that the “window of impairment” is three to 10 hours based on “moderate to high doses” of THC.

That said, authors of the latest study suggest “further research is warranted to understand cannabis- and alcohol-involved MVC fatalities.”

Notes Lira: ”The bottom line is that we have a lot of work to do to reduce deaths and harms from impaired driving from alcohol, cannabis, and other substances.”

A Canadian study published this summer shows that neither Ontario nor Alberta — the two provinces with the most cannabis retail stores in the country — saw a significant rise in emergency visits from traffic-related injuries recreational cannabis was green-lit three years ago.

And a Colorado study, where recreational cannabis is legal, did not find many differences between regular and occasional weed users once behind the wheel.

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