A new study suggests these biomarkers are inconsistent indicators.
The findings contrast with the much stronger relationship between blood alcohol concentrations and driving impairment, with implications for the application of drug-driving laws globally.
Researchers at the University of Sydney’s Lambert Initiative have analysed all available studies on the relationship between driving performance and concentrations in blood and saliva of tetrahydrocannabinol (THC), the intoxicating component of cannabis.
The surprising results indicate that blood and oral fluid THC concentrations are relatively poor or inconsistent indicators of cannabis-induced impairment.