10 Things Wrong with the Latest Cannabis Traffic Study

We have yet another study claiming that cannabis-related traffic injuries have increased since Canada legalized cannabis.

The research, published in JAMA Network Open, looked at cannabis and emergency room visits for traffic injuries between 2010 and 2021 in Ontario.

“Our data is raising concern about a growing problem of cannabis impairment and severe road injuries,” said lead author Dr. Daniel Myran. “Since 2010, there has been a very, very large increase in cannabis involvement and traffic injury visits in Ontario.”

But has there been? Or is this a case of increased reporting since legalization?

Let’s give Dr. Myran the benefit of the doubt. Let’s assume that cannabis-related traffic injuries have increased since legalization.

Does this study prove it? 

Not by a long shot. There are at least ten things wrong with this latest cannabis traffic study.

Ten Things Wrong with the Latest Cannabis-Traffic Study

In scientific inquiry, the gold standard is randomized control trials (RCTs). An RCT establishes cause and effect. This latest cannabis traffic study was not an RCT.

10. Lack of Randomization

This observational study cannot establish a direct cause-and-effect relationship between cannabis legalization and traffic injury ED visits. Without randomization, the researchers cannot rule out confounding variables.

Like, for example, whether legalization means people are more comfortable reporting their cannabis use. As opposed to before, if you’re in an emergency room for a traffic accident, no way in hell would you admit you were consuming illegal drugs right before the incident.

9. Causality in Cannabis Traffic Study

This study looks at different periods (pre-legalization, legalization before edibles, legalization “commercialization”) and changes in traffic injury ED visits. But, as mentioned, nowhere in the study do the authors establish a clear causal link.

Let’s reiterate that. You might have been given a different impression because of media headlines and quotes from the lead author. This study does not establish a causal link between cannabis legalization and increased ED visits.

They ignore entirely other factors, such as changes in enforcement and public awareness. These are two significant factors to consider. Law enforcement has far more tools to detect stoned drivers than they did before 2018. 

As well, busybodies who can’t yell at people for not wearing masks anymore have to focus their attention elsewhere. Narcing on suspected stoned drivers is one outlet. Even well-intentioned individuals might call the authorities if they believe a stoned driver is dangerous to themselves or others on the road.

8. Control Group 

This study uses alcohol-involved traffic injury ED visits as a control group. There are several problems with this. One, like the above problem, control groups may be influenced by external factors, such as changes in alcohol consumption patterns.

Two, without a genuinely inert control group, the authors cannot attribute changes solely to cannabis legalization. A control group is supposed to provide a baseline or reference point against which the researchers can compare the effects of an intervention (or exposure).

For this study’s control group to be helpful, researchers would need a control group that experiences no changes from cannabis legalization. Of course, that’s easier said than done. Hence, observational studies like this one use a “similar” control group. 

The idea is to control for as many variables as possible and adjust for confounding factors. While this approach may help researchers draw conclusions, it can’t establish causation. It does not justify some of the statements people make about this study.

Ten Things Wrong with the Latest Cannabis Traffic Study

7. Data Sources Used in Cannabis Traffic Study

Like most studies, they rely on administrative and bureaucratic databases for their information. However, these databases can introduce biases and inaccuracies. From underreporting to misclassification. All of which affect the study’s validity.

For example, the study does not list which strains were more likely to “cause” traffic accidents. As well, what about the cannabinoid content? And how was some of this information collected? If I’m in a traffic accident, but there’s THC in my system from an edible I ate 48 hours before, will nurses check the “cannabis” box?

What if police find a bunch of CBD joints in my car, and I admit I was smoking before the accident? Do hospital admin staff know the differences between the various cannabinoids and their effects? Or is everything just lumped under “cannabis?” 

6. Ecological Fallacy

One of this study’s more egregious claims comes from concluding individual behaviour from population-level data. This is known as the ecological fallacy, where someone makes inferences about individuals based on group-level data.

The researchers of this study did not consider individual-level factors, attitudes, and behaviours related to cannabis consumption and driving. 

Depending on your philosophical worldview, methodological individualism is the only proper method of the social sciences, which makes this cannabis traffic study even more useless than it already was.

5. Temporal Confounding in Cannabis Traffic Study

This cannabis-traffic study links cannabis legalization to increases in traffic ED visits. However, some of their data is confounded by covid restrictions affecting mobility, traffic, and healthcare resources. In research circles, we call this temporal confounding.

One of the best (and most common) examples is the relationship between ice cream sales and drownings at a local beach. You can observe that as ice cream sales increase, so does the number of drownings.

Suppose you were one of the authors of this cannabis traffic study. You’d probably conclude that eating ice cream causes an increase in drownings. However, when you consider the seasons, you realize ice cream sales and beach drownings increase during summer.

It’s not ice cream causing drownings. It’s the weather driving both variables. Now, consider this cannabis traffic study.

The increase in cannabis-involved traffic injury ED visits occurred during the “commercialization” phase of legalization. But that also coincided with covid-19 (March 2020 to December 2021).

During the pandemic, people altered their travel patterns, work situations, relationships, and healthcare-seeking behaviours. These changes might have affected the likelihood of traffic injuries and the reporting of cannabis involvement.

Temporal confounding makes it impossible to attribute the observed increase solely to cannabis commercialization. Without considering the pandemic’s effects, the study overestimates the impact of cannabis commercialization on traffic injuries.

4. Limited Scope

This cannabis-traffic study focuses on associating cannabis legalization with traffic injury ED visits. It doesn’t delve into other factors, such as changes in road safety measures, increased construction, increased traffic, poor driver education, or public awareness campaigns.

It also doesn’t consider that substances, like cannabis or alcohol, are proximate causes of traffic injury ED visits. The ultimate cause is the road owner’s irresponsible road management.

Blaming cannabis is like blaming bullets for a mass shooting. You don’t blame the inanimate object. You condemn the conscious agent making the choice.

Ten Things Wrong with the Latest Cannabis Traffic Study

3. Generalizability

This study is specific to Ontario, Canada. It may not apply to regions with different legalization policies and traffic regulations. 

2. Sample Size 

This cannabis traffic study and the media headlines are forgoing one crucial fact. Cannabis-involved traffic injury ED visits are rare. They represent 0.04% of all visits. Not only is this a non-issue, but the sample size is too limited for the researchers to make these false claims.

1. Ethical Considerations in Cannabis Traffic Study

As mentioned, this study relied on administrative and bureaucratic databases for their information. Databases that can introduce biases and inaccuracies.

But more so, using healthcare data without informed consent raises ethical concerns. If you’re concerned about the potential for privacy breaches, you should lie to your doctor or healthcare professional.

Don’t want your cannabis use to be a statistic in the latest reefer madness study? Lie to your doctor or healthcare professional.

Of course, this creates its own set of problems. This is why researchers should not be using this data without informed consent. 

And they certainly shouldn’t be drawing causal conclusions from observational research. 

Ten Things Wrong with the Latest Cannabis Traffic Study

This cannabis traffic study may provide some insights into trends. But that’s all it would be. An observed trend that is limited by methodology and confounding factors.

So you can safely ignore the “475% increase in cannabis-related traffic accidents” headline making its way through the corporate press.

No causal relationship exists between cannabis legalization and cannabis-involved traffic injury ED visits in Ontario. Full stop.

However, discovering the truth was not the goal of this study. Like so much of modern “Science,” the goal is to influence policy. As the study concludes,

Our findings suggest that measures to control access to cannabis products and stores may help prevent cannabis involvement in traffic injuries.

In other words, our faulty study ignores the failure of road socialism. Instead, it suggests we’ll have to limit an already restricted cannabis market.

For your own good, of course.