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Indeterminacy of Cannabis Impairment and ∆9-Tetrahydrocannabinol (∆9-THC) Levels in Blood and Breath

Michael W. DeGregorio, Gregory T. Wurz

preprint DOI: 10.21203/rs.3.rs-1300672/v1 (opens in new tab)

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Study at a glance

AI-extracted from the abstract
Characteristics Observational study
Sample size 34
Population Cannabis smokers providing blood and exhaled breath samples
Measures horizontal gaze nystagmus
Topics Cannabis
Key findings Single measurements of D9-THC in blood, and now in exhaled breath, did not correlate with impairment following inhalation; 16 of 30 subjects exceeded 5 ng/mL after 12 hours of abstinence without impairment. The authors suggest other cannabinoids, including cannabigerol, cannabichromene, and D9-tetrahydrocannabivarin, may be key indicators of recent cannabis inhalation.

Abstract

Abstract: Previous investigators have found no clear relationship between specific blood concentrations of D9-tetrahydrocannabinol (D9-THC) and impairment, and thus no scientific justification for use of legal “per se” D9-THC blood concentration limits. Analyzing blood from 30 subjects showed D9-THC concentrations that exceeded 5 ng/mL in 16 of the 30 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 D9-THC levels were related to increasing blood levels in the absence of impairment, suggesting that single measurements of D9-THC in breath, as is blood, are not related to impairment. When post-smoking duration of impairment was compared to baseline D9-THC blood concentrations, subjects with the highest baseline D9-THC levels tended to have the shortest duration of impairment. It was further shown that subjects with the shortest duration of impairment also tended to have the lowest incidence of horizontal gaze nystagmus at 3 h post-smoking. Finally, analysis of breath samples from these subjects revealed the presence of transient cannabinoids such as cannabigerol, cannabichromene, and D9-tetrahydrocannabivarin during the peak impairment window, suggesting that these compounds may be key indicators of recent cannabis use through inhalation. In conclusion, these results provide further evidence that single measurements of D9-THC in blood, and now in exhaled breath, do not correlate with impairment following inhalation, and that other cannabinoids may be key indicators of recent cannabis inhalation.

Comparable studies

Other observational and cohort studies on cannabis, most cited first.

Study Year Design Participants
High-potency cannabis and the risk of psychosis People with first episode of psychosis and healthy controls from the local population 2009 Case-control study n = 454
Ayahuasca-Assisted Therapy for Addiction: Results from a Preliminary Observational Study in Canada Rural aboriginal population 2013 Observational study
Impaired cognitive performance in drug free users of recreational ecstasy (MDMA) Otherwise healthy young people 2000 Observational
Continued cannabis use and risk of incidence and persistence of psychotic symptoms: 10 year follow-up cohort study Individuals from the general population in Germany aged 14-24 at baseline 2011 Observational cohort n = 1,923
Cannabis-induced psychosis and subsequent schizophrenia-spectrum disorders: follow-up study of 535 incident cases Patients treated for cannabis-induced psychotic symptoms in Denmark between 1994 and... 2005 Observational cohort n = 535

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