Car crash deaths involving both cannabis and alcohol more than doubled

3rd November 2021

New research indicates that between 2000 and 2018, the percentage of car crash deaths in the United States involving cannabis have doubled, and the percentage of deaths involving both cannabis and alcohol, have more than doubled.

According to a study published in the American Journal of Public Health, the loosening of cannabis policies in many states has coincided with a rise in people using cannabis and alcohol before going behind the wheel.

The researchers analysed 19 years of data from the Fatality Analysis Reporting System, a national database of fatal crashes on public roads.

The number of crash deaths involving cannabis more than doubled from 9% in 2000 to 21.5% in 2018, and the percentage of deaths involving both cannabis and alcohol also more than doubled from 4.8% to 10.3%. The authors of the study concluded that cannabis was a risk factor for alcohol co-involvement, even at low levels below the legal limit.

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

The data also show that car crashes involving cannabis are more likely to result in the death of passengers and those aged under 35 in comparison to crash fatalities not involving cannabis.

The researchers carried out a series of analyses to account for drug testing rates and alcohol laws and policies, however, the results remained consistent.

Marlene Lira, MPH, an epidemiologist at Boston Medical Center and lead author on this study, said: “Our testing methods for cannabis remain suboptimal, and individuals can test positive for cannabis weeks after they have consumed it.

“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.

”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.”

In addition to these findings, as Canex reported last year, a study found that shortly after local governments had legalised the recreational use of cannabis in three American states, the number of road traffic accidents rose by an average of one additional traffic fatality per million residents.

However, these numbers mirrored the neighbouring jurisdictions during the examined period of time.

Therefore, while driving under the influence of cannabis may increase the risk of being involved in a road traffic accident, it appears that cannabis legalisation does not lead to large or sustained increases in traffic accidents.

In contrast, in research published in The Journal of Law and Economics, scientists found “a noticeable drop in traffic fatalities following legalisation.”

While research is ongoing and existing findings are often contradictory, it is widely agreed that driving under the influence of any mind-altering substances – legal or not – cannot be justified.

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