Marijuana Moment
A federal traffic safety agency says that there’s “relatively little research” backing the idea that THC concentration in the blood can be used to determine impairment, calling into question laws in several states that set “per se” limits for cannabinoid metabolites.
In a draft report posted last month, the National Highway Traffic Safety Administration (NHTSA) discussed mixed scientific findings about marijuana and driving but questioned the broader concept of impairment testing that’s based on THC content in a person’s system.
“Several states have determined legal per se definitions of cannabis impairment, but relatively little research supports their relationship to crash risk,” the report says. “Unlike the research consensus that establishes a clear correlation between [blood alcohol content] and crash risk, drug concentration in blood does not correlate to driving impairment.”
While NHTSA pointed to certain studies that it said supports the idea that cannabis use may increase the risk of traffic accidents, it also noted additional research that “did not find a significant correspondence” between marijuana and how police assign responsibility for accidents.
The report’s point about per se THC limits is consistent with recent comments from a Justice Department researcher who said that states may need to “get away from that idea” that marijuana impairment can be tested based on the concentration of THC in a person’s system.
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