Research roundup: Studies look at impact of weed and alcohol on driving

Effects on subjects’ performance following ingestion of alcohol and cannabis together was greater than the effect of each drug by itself


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A new study out of New Jersey suggests that there is no clear link between cannabis legalization and cannabis use detected in motor-vehicle crash patients.

Researchers from Hackensack University Medical Center compared patient data from states with cannabis and those without over a period of 12 years (2006 to 2018). They also compared the percentage of patients who tested positive for THC  to the percentage of patients who drove under the influence of alcohol.

“There did not appear to be a relationship between the legalization of marijuana and the likelihood of finding THC in patients admitted after MVC (a motor vehicle crash),” the authors concluded.

The study, published in The American Surgeon, found that the rate of cannabis apparent in crash patients did increase, but not just in states with legal weed. It increased across the board

“In fact, in Texas, where marijuana remains illegal, there was the largest change in detection of THC,” the study states.

The researchers concluded: “There was no apparent increase in the incidence of driving under the influence of marijuana after legalization. In addition, the changes in marijuana legislation did not appear to impact alcohol use.”

Booze and pot are more potent together

Another study on the connection between substance use and impaired driving found that ingesting inhaled cannabis and alcohol simultaneously affected simulated driving performance more than consuming either substance alone.

Researchers affiliated with the University of Toronto published their data in the journal Psychopharmacology.

As reported by NORML, the investigators “assessed simulated driving performance in 28 subjects following their use of placebo alcohol and placebo cannabis (<0.1 percent THC), alcohol and placebo cannabis, placebo alcohol and active cannabis, and alcohol and active cannabis”.

The researchers tested participants on their ability to maintain lateral positioning and speed in a driving simulation. They also tested subjects’ reaction time.

The study’s authors reported that the effects on subjects’ performance following ingestion of both booze and weed together “was significantly greater than the effect of each drug by itself”.

The investigators noted that earlier research had “provided some evidence for an additive effect of the combination of cannabis and alcohol on driving measures and the current results…support these findings.”

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