Marijuana Influenced Drivers more Likely to have a Fatal Vehicle Crash
Marijuana users are found in a new study to be more than twice as likely to be involved in a vehicle crash; especially a fatal collision.
The finding comes from a review of multiple studies showing cannabis consumption within three hours of driving - without alcohol or other drugs on board - can raise the chances of collision.
Researchers from Dalhousie University reviewed nine studies with a total sample of 49,411 people. Results were taken from blood sample or self-reported marijuana use.
Most of the studies used 1 ng/ml of cannabis or any amount greater than zero as the cutoff for a positive test result. One study used self-reporting and another used 2g/ml.
The authors looked at just the effects of marijuana on driving reactions, excluding any effects from alcohol or other drugs for the analysis.
Criteria for a vehicle crash was “a collision or incident that may or may not lead to injury, occurring on a public road and involving at least one moving vehicle”; defined by the World Health Organization.
All of the accidents included one or more moving vehicles of all types that took place on a public road.
Seven out of nine studies found marijuana use within a few hours of driving raises the risk of having a collision. Two studies concluded the risk of a motor vehicle accident from cannabis use was lower than that of unimpaired drivers.
The reviewers for the study write, “Most studies in our meta-analysis consistently showed an increased effect of cannabis use on the risk of motor vehicle collisions.”
They also found fatal crashes were more likely from higher doses of tetrahydrocannabinol in the blood, compared to non-fatal injuries.
The researchers say the results could be limited by other cofounders that were “probably” not controlled for in the medium to high quality studies used in the analysis.
The finding could be used for public education and by policy makers.to control drug use while driving. The authors concluded marijuana use is associated with increased risk of motor vehicle crash, especially fatal accidents.