A new study published in Neuroscience & Biobehavioral Reviews, conducted by researchers at the University of Sydney’s Lambert Initiative, looked into available reports on the relationship between driving performance and concentrations in blood and saliva of tetrahydrocannabinol (THC), the intoxicating component of cannabis.
Surprisingly, the results indicate that blood and oral fluid THC concentrations are relatively poor or inconsistent indicators of cannabis-induced impairment. This contrasts with the much stronger relationship between blood alcohol concentrations and driving impairment. The findings have implications for the application of drug-driving laws globally, the researchers say.
‘No Significant Relationship’
“Higher blood THC concentrations were only weakly associated with increased impairment in occasional cannabis users while no significant relationship was detected in regular cannabis users," McCartney said. “This suggests that blood and oral fluid THC concentrations are relatively poor indicators of cannabis-THC-induced impairment.”
For the study, researchers pooled data from 28 publications involving the consumption of either ingested or inhaled forms of cannabis. They then characterized the relationships between blood and oral fluid THC concentrations and driving performance – or driving-related skills such as reaction time or divided attention.
For infrequent, or occasional cannabis users, some significant correlations between blood and oral fluid …