Are blood and oral fluid Δ9-tetrahydrocannabinol (THC) and metabolite concentrations related to impairment? A meta-regression analysis

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McCartney, D
Arkell, TR
Irwin, C
Kevin, RC
McGregor, IS
Griffith University Author(s)
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2022
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http://creativecommons.org/licenses/by-nc-nd/4.0/
Abstract

Blood and oral fluid Δ9-tetrahydrocannabinol (THC) concentrations are often used to identify cannabis-impaired drivers. We used meta-analytic techniques to characterise the relationships between biomarkers of cannabis use, subjective intoxication, and impairment of driving and driving-related cognitive skills. Twenty-eight publications and 822 driving-related outcomes were reviewed. Each outcome was measured in concert with one or more biomarkers of cannabis/THC use and/or subjective intoxication. Higher blood THC and 11−OH-THC concentrations, oral fluid THC concentrations and subjective ratings of intoxication were associated with greater impairment in ‘other’ (mostly occasional) cannabis users (p's<0.05). Blood 11−COOH-THC concentrations were associated with impairment after inhaling, but not orally ingesting, cannabis/THC. However t these ‘biomarker–performance’ relationships (R) were only very weak (blood THCpost-ingestion: -0.08; blood THCpost-inhalation: -0.10; blood 11−OH-THCpost-ingestion: -0.13), weak (blood 11−OH-THCpost-inhalation: -0.24; oral fluid THCpost-inhalation: -0.36; subjective intoxication: -0.29) or moderate (blood 11−COOH-THCpost-inhalation: -0.43) in strength. No significant biomarker-performance relationships were observed in ‘regular’ (weekly or more often) cannabis users (p's>0.10), although the analyses were less robust. Blood and oral fluid THC concentrations are relatively poor indicators of cannabis/THC-induced impairment.

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Neuroscience and Biobehavioral Reviews
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134134
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© 2022 The Author(s). Published by Elsevier Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International (CC BY-NC-ND 4.0) License, which permits unrestricted, non-commercial use, distribution and reproduction in any medium, providing that the work is properly cited.
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Neurosciences
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McCartney, D; Arkell, TR; Irwin, C; Kevin, RC; McGregor, IS, Are blood and oral fluid Δ9-tetrahydrocannabinol (THC) and metabolite concentrations related to impairment? A meta-regression analysis, Neuroscience and Biobehavioral Reviews, 134, pp. 104433, 2022
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