A Monday press release from the government of Manitoba contained a single, shocking statistical claim about the risks of marijuana-impaired driving.
"The Office of National Drug Control Policy found in Colorado, during the four-year period following legalization in 2013, that cannabis-related driving deaths increased by 66 per cent when compared to the four-year period prior to legalization," said the press release, which described Premier Brian Pallister's trip to meet impaired driving researchers at the University of Iowa.
"We’re not going to let the U.S. stats become our stats," said Pallister in the release.
But that terrifying U.S. statistic is in fact highly misleading, experts say, and should not be considered an accurate assessment of whether legalizing cannabis results in more traffic deaths.
The claim that "cannabis-related driving deaths increased by 66 per cent" in Colorado after legalization comes from a 2017 report published by the Rocky Mountain High Intensity Drug Trafficking Area, a U.S. federal law enforcement task force funded by the White House's Office of National Drug Control Policy.
"As a result of that, it's unsurprising that most of the information that the report puts out paints cannabis use, and the effects of cannabis use, in light of dangers and in light of social problems," said John Hudak, a senior fellow at the nonpartisan Brookings Institution who studies marijuana policy in the U.S.
Although Hudak said some information in the Rocky Mountain High Intensity Drug Trafficking Area report is accurate, he warned that "the politicization of some of the data, and the inapproriate manner of analysis, overshadows the more positive parts of the report."Advertisement
While the link between cannabis legalization and traffic safety is an important public policy issue, Hudak said, the specific statistic cited by the government of Manitoba "is misleading on its face" and "probably inappropriately declares a public safety outcome that may or may not be there."
"I think if you read that statistic, you would think, 'Well, impaired drivers are causing crashes,'" said Hudak. "Those data do not include exclusively impaired drivers. And that's a problem."
In a footnote, the Rocky Mountain High Intensity Drug Trafficking Area report acknowledges that the term "marijuana-related... does not necessarily prove that marijuana was the cause of the incident." Later, the report says "marijuana-related" simply refers to "any time marijuana shows up in the toxicology report."
Because traces of cannabis can remain in a user's body long after the effects of the drug wear off, the presence of marijuana in a toxicology report doesn't mean a driver was impaired by cannabis at the time of a traffic incident.
"So you're not actually tracking accidents that are related to cannabis, let alone accidents where cannabis caused the accident by impairing the driver," said Jacob Sullum, a senior editor with Reason Magazine who has covered U.S. drug policy for decades and reported on the agenda pushed by the Rocky Mountain High Intensity Drug Trafficking Area's reports.
The Office of National Drug Control Policy is actually required under U.S. federal law to oppose the legalization of drugs, explained Sullum.
"Telling the truth is problematic for them, to the extent that the truth undermines the case for prohibition," said Sullum. "And I think people are starting to wise up to that. You still will see those reports cited uncritically, but not as often as before."
In reality, gathering reliable data on whether cannabis legalization in U.S. states like Colorado has impacted road safety is incredibly complicated, said Hudak.
"One of the challenges in this space is that states don't have great baseline sources of data, pre-legalization. And so once legalization happens in states, states begin collecting more data, or collecting data differently."
Comparing newer, more robust data on drug-impaired collisions to weaker, pre-legalization data is effectively comparing apples to oranges.
"Being able to make points that are accurate and convincing and sound with public policy data is not as easy as comparing two percentages, usually," said Hudak.
Still, the question of whether cannabis legalization increases traffic deaths remains — and various researchers have drawn conflicting conclusions. Hudak said other researchers take a "more responsible approach" than the report referenced in the Manitoba government's press reelase, citing a new working paper by the National Bureau of Economic Research.
The authors of that report used advanced statistical methodologies to test the causal impact of recreational marijuana legalization on traffic fatalties in Colorado and Washington against a control group of states where the drug is still illegal.
"Our estimates yield little evidence to support the notion that the legalization of recreational marijuana caused traﬃc fatalities to double, as has been suggested in the media," said the NBER report.
Canadians who read U.S. reports about the impacts of cannabis legalization, said Hudak, should try to learn where the data originally came from.
"Is it an interest group with an agenda? Is it a government agency with an agenda? Is it a politically motivated entity? On the flipside, is it industry? Is it advocacy communities in favour of cannabis?"
"Those groups are not necessarily, by default, putting out bad information, but you have to think about the motives behind the information that they put out," said Hudak.
Last week, Pallister's government unveiled a new bill that will subject Manitoba drivers to provincial sanctions for drug-impaired driving, on top of new criminal penalties being proposed by the federal government to coincide with the legalization of cannabis.
A spokesperson for Premier Pallister's office said the government of Manitoba "is taking a responsible approach to legalized cannabis and part of that approach is collecting as much available information as possible."
"Our government’s efforts on preparing for legalized cannabis are not solely motivated by the limited statistics available on the subject," the spokesperson said in a statement.
"The fact is that no one can dismiss the impacts of drug impaired driving as a significant policy concern."