Authors
Matthew A Albrecht, Razi Hasan, Damir Kekez and Huaqiong Zhou
Published
March 28 2025
Abstract
A recent meta-analysis in Drug Science, Policy and Law on the risk associated with the detection of tetrahydrocannabinol (THC) in blood and crash risk indicated a ∼10–70% increase in crash culpability for detection of THC. However, this and previous meta-analyses did not analyse a dose-response relationship between blood concentrations of THC and risk necessary to better understand the crash risk associated with THC. This would inform public risk tolerances surrounding THC and driving. Here, we conducted a meta-regression to identify the blood concentration crash culpability risk relationship. Crash culpability risk increases with increasing THC concentration, with an inflection around 1.5–3.0 ng/ml where risk begins to increase. There is a doubling of culpability risk around 5 ng/ml and a potential quadrupling of risk around 10 ng/ml. Conversely, blood THC concentrations below ∼1.5 ng/ml indicate practically no culpability risk (<30% increase). More studies are needed to better define risk for the lower and higher bands of blood THC concentrations. Consideration of blood concentration risk relationships is necessary for public discussions surrounding THC and crash risk.
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