One of the long-standing beliefs about marijuana is that it makes people much more likely to get into a car crash. Now, a brand new study has said this idea is based on faulty statistics.
As just one example, here’s Floria Representative John Mica testifying about what he sees as the dangers of marijuana. His presentation was made at a congressional hearing in 2014:
Representative Mica claimed that “in the last dozen years we’ve had a quarter of a million Americans slaughtered on the highways . . . and half of those fatalities are related to people who are impaired through alcohol or drugs.”
He pinpointed marijuana as an especially troubling substance:
“And as we embark on this new era with many more people exposed to what is still a Schedule I narcotic, we are going to have a lot more people stoned on the highway.”
The idea that people who use marijuana are more likely to become dangerous behind the wheel stems primarily from a couple well known studies. They were both published in 2012.
One of them claimed that there is a 92% increase in the risk of getting into a crash when a driver has used marijuana.
The other one concluded that marijuana increased the likelihood of getting into a crash by 166%.
But now, a group of researchers led by Ole Rogeberg and Rune Elvik is about to publish a brand new study that refutes both of those claims.
In the new article, which is scheduled for publication in an upcoming issue of the journal Addiction, researchers analyzed both of the studies mentioned above.
Through their analysis, they concluded that there were “methodological shortcomings” in the original studies that could have produced inaccurate conclusions.
Rogeberg and Elvik said that the article claiming a 92% increase in crashes didn’t take into account some important data. In particular, the original study analyzed groups of drivers who are already more likely to get into car crashes regardless if marijuana was involved.
When that is taken into account, Rogeberg and Elvik said, the stats look very different.
“Study 1 substantially revises previous risk estimates downwards,” the new article said.
When they looked at the study that claimed a 166% increase in crashes, Rogeberg and Elvik said the numbers were skewed because there were problems with how the study was carried out.
“The lack of clear study selection criteria . . . gives the resulting pooled estimate no meaningful interpretation,” they wrote.
Rogeberg and Elvik ultimately conclude that marijuana does have a limited impact on how well a person drives. But the numbers produced by earlier studies are hugely overexaggerated.
So much so, in fact, that they can create a skewed image of the supposed dangers of marijuana.
Last year, the National Highway Traffic Safety Administration did its own study of marijuana’s impact on drivers. The findings of this study seem to line up pretty well with Rogeberg’s and Elvik’s conclusions.
The NHTSA concluded that “consuming marijuana does not elevate the crash risk of the driver” in any significant way.
(Photo Credit: thefreethoughtproject)