Researchers at Columbia University found that marijuana use can increase the risk of having a car accident by as much as 166%. The findings of this study have been used time and again by marijuana prohibitionists and the media sources alike. Fortunately, there are researchers out there that are willing to take a more in-depth look at findings like these and their discoveries are alarming.
Numbers don’t lie
According to a recent analysis published in the journal Addiction, the increase in crash risk while using marijuana is only about 20-30% as opposed to the 92% risk increase proposed by a 2012 British Medical Journal (BMJ) report.
Researchers Ole Rogeberg and Rune Elvik performed a new meta-analysis of the BMJ analysis considering additional confounding variables. The study took a closer look at the individuals that represented the data used for the original BMJ analysis.
“Using cannabis and driving under the influence are behaviors that are more common among young adults and males, groups with higher crash risks irrespective of use. Estimated odds ratios typically decline substantially after adjustments for such factors.” – Rogeberg and Elvik
Young males are always at risk to have car accidents
When taking into consideration that young males are more likely to have car accidents in general, the relationship between marijuana use and car accidents drops significantly—this is the main difference between the new study and the old.
Rogeberg and Elvik didn’t stop at re-examining the BMJ analysis; they also dug into another study. A 2012 analysis done by Mu-Chen Li and other researchers at Columbia University, found that marijuana use increased car crash risk by 166%.
Rogeberg and Elvik found that “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.”
When considering the obtuse nature of these confounding variables, Rogeberg and Elvik determined that “the lack of clear study selection criteria…gives the resulting pooled estimate no meaningful interpretation.”
Third time’s a charm
Rogeberg and Elvik successfully dispelled 2 potentially damning studies, so they decided to create their own original analysis. They examined 21 other data sets and replicated the studies of Li et al. and the BMJ analysis. Using those 2 unique statistical methods, they found that the risk increase of car accidents when using marijuana was 22% and 36% respectively.
Their findings in the new studies reported an increase of car accident risk from marijuana use to be in line with the risk associated with a blood alcohol concentration of .05%. This is less than the legal blood alcohol content of .08%. They propose that only 20-30% of accidents are caused because of cannabis use while nearly 85% of accidents involving alcohol are caused because of the alcohol use.
It took some heavy statistical analysis involving scary words like regression and standard deviation, but Rogeberg and Elvik were able to overcome the misinformation perpetuated by prohibitionists. If you don’t have time to dig through the heavy analysis presented by these geniuses, you can rest assured that the truth is now out there. I wouldn’t suggest driving while you are high if you can help it, but statistically it isn’t that dangerous.
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