Driving High Not as Dangerous as Previously Believed


With marijuana now legal in 23 states, Washington D.C., Guam, and more states on their way to voting about legalization this year, more questions about driving high have surfaced. The risk of getting into an accident while driving stoned was thought to be very high due to a BMJ study conducted in 2012. This has created a potential factor to consider both federally and for each state as the issue of marijuana legalization comes up more frequently.

The Original Research

Still not advisable, obviously.

Ole Rogeberg of the Ragnar Frisch Center for Economic Research and Rune Elvik of the Norwegian Center for Transport Research in Oslo, did a study of a 2012 BMJ meta-analysis by Canadian epidemiologist Mark Asbridge and two of his colleagues at Dalhousie University in Halifax. The initial BMJ article showed that crashes were 92% more likely under the influence of marijuana. Rogeberg and Elvik found that after reviewing the study and taking all factors into consideration, the correct percentage was more like 20-30%. This is a vast difference from what was initially reported.

The Opposition of Recent Research

The reason for the difference in calculation is based on one fairly prominent consideration. Young men below a certain age are more likely to get into an accident regardless of whether they are intoxicated or not. Their behavior on the roads is statistically a lot more reckless and they are generally considered a high risk group for accidents. When Rogeberg and Elvik looked at the factors of age and gender and recalculated the studies, they found that the risk of getting into a car accident while driving high was low to moderate and a much lower percentage than previously thought.

Research With Meaningless Interpretation

Luckily, the driver seat is empty.

Other studies done at Columbia University showed the increased risk of crash at 166%. Rogeberg and Elvik took a look at the studies and according to them “the pooled studies report qualitatively different types of associations: Self-reported crashes in some past period for cannabis ever-users vs. never-users, self-reported crashes in a past period for those with self-reported intoxicated driving episodes in the past vs. those without, and acute intoxication amongst crash-involved and other motorists.” They conclude that “the lack of clear study selection criteria…gives the resulting pooled estimate no meaningful interpretation.”

Scrutinizing the Testing of THC in Motorists

Rogeberg and Elvik decided to conduct a new meta-analysis of 21 studies. This new review created two different estimates, each based on a different statistical method. The first estimate generated a result of 22% risk increase and the other statistical method generated a result of 36% increased risk. They concluded that the previous studies overestimated their results based on the subjects being pooled. A 2015 National Highway Traffic Administration study showed no association between marijuana use and car crashes. This may be because THC can remain in the blood for some time, even when a person isn’t feeling the effects. Therefore, a lot of road testing for THC is subject to scrutiny when it comes to determining a person’s driving ability.

Knowing the true risk involved in driving stoned can help users make more informed assessments when it comes to getting behind the wheel. Perhaps now, with a more accurate perspective of the actual risks involved in driving high, both the federal and state governments will be set more at ease with the notion of legalization.


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