Are blood and oral fluid Δ9-tetrahydrocannabinol (THC) and metabolite concentrations related to impairment? A meta-regression analysis
9 February, 2022
Study results indicate blood and oral fluid (saliva) THC concentrations are relatively poor or inconsistent indicators of cannabis-induced impairment. A cannabis-inexperienced person can ingest a large oral dose of THC and be completely unfit to drive yet register extremely low blood and oral fluid THC concentrations, whilst an experienced cannabis user might smoke a joint, show very high THC concentrations, but show little if any impairment.
University of Sydney, Lambert Initiative for Cannabinoid Therapeutics, Brain and Mind Centre, Faculty of Science School of Psychology, Sydney, New South Wales; Centre for Human Psychopharmacology, Swinburne University of Technology, Melbourne, Victoria; Menzies Health Institute Queensland and School of Health Sciences and Social Work, Griffith University, Gold Coast, Queensland, Australia.
Indeterminacy of cannabis impairment and ∆9-tetrahydrocannabinol levels in blood and breath
May 2022
Previous investigators found no clear relationship between specific blood concentrations of ∆9-THC and impairment, and thus no scientific justification for use of legal ‘per se’ ∆9-THC blood concentration limits. Analysing blood showed ∆9-THC concentrations that exceeded 5 ng/mL in subjects following a 12-hour period of abstinence in the absence of any impairment. In blood and exhaled breath samples collected from a group of 34 subjects at baseline prior to smoking, increasing breath ∆9-THC levels were correlated with increasing blood levels in the absence of impairment, suggesting that single measurements of ∆9-THC in breath, as in blood, are not related to impairment.
Cancer Immunotherapy Research Institute, Roseville, California, United States.
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