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Can inhaled cannabis users accurately evaluate impaired driving ability? A randomized controlled trial
Sarah Hartley1, Nicolas Simon2, Bibiana Cardozo2
1Sleep Unit, Physiology Department, AP-HP GHU Paris-Saclay, Raymond Poincaré Hospital, Garches, France.
Aims:
To study the effect of inhaled cannabis on self-assessed predicted driving ability and its relation to reaction times and driving ability on a driving simulator.
Participants And Methods:
30 healthy male volunteers aged 18-34: 15 chronic (1-2 joints /day) and 15 occasional (1-2 joints/week) consumers. Self-assessed driving confidence (visual analog scale), vigilance (Karolinska), reaction time (mean reciprocal reaction time mRRT, psychomotor vigilance test), driving ability (standard deviation of lane position SDLP on a York driving simulator) and blood concentrations of delta-9-tétrahydrocannabinol (THC) were measured before and repeatedly after controlled inhalation of placebo, 10 mg or 30 mg of THC mixed with tobacco in a cigarette.
Results:
Cannabis consumption (at 10 and 30 mg) led to a marked decrease in driving confidence over the first 2 h which remained below baseline at 8 h. Driving confidence was related to THC dose and to THC concentrations in the effective compartment with a low concentration of 0.11 ng/ml for the EC50 and a rapid onset of action (T1/2 37 min). Driving ability and reaction times were reduced by cannabis consumption. Driving confidence was shown to be related to driving ability and reaction times in both chronic and occasional consumers.
Conclusions:
Cannabis consumption leads to a rapid reduction in driving confidence which is related to reduced ability on a driving simulator.
Clinical Trial Registration:
ClinicalTrials.gov, identifier: NCT02061020.
