Abstract
BackgroundThe main psychoactive component of cannabis, delta-9-tetrahydrocannabinol (THC), can impair driving performance. Cannabidiol (CBD), a non-intoxicating cannabis component, is thought to mitigate certain adverse effects of THC. It is possible then that cannabis containing equivalent CBD and THC will differentially affect driving and cognition relative to THC-dominant cannabis.AimsThe present study investigated and compared the effects of THC-dominant and THC/CBD equivalent cannabis on simulated driving and cognitive performance.MethodsIn a randomized, double-blind, within-subjects crossover design, healthy volunteers (n = 14) with a history of light cannabis use attended three outpatient experimental test sessions in which simulated driving and cognitive performance were assessed at two timepoints (20–60 min and 200–240 min) following vaporization of 125 mg THC-dominant (11% THC; < 1% CBD), THC/CBD equivalent (11% THC, 11% CBD), or placebo (< 1% THC/CBD) cannabis.Results/outcomesBoth active cannabis types increased lane weaving during a car-following task but had little effect on other driving performance measures. Active cannabis types impaired performance on the Digit Symbol Substitution Task (DSST), Divided Attention Task (DAT) and Paced Auditory Serial Addition Task (PASAT) with impairment on the latter two tasks worse with THC/CBD equivalent cannabis. Subjective drug effects (e.g., “stoned”) and confidence in driving ability did not vary with CBD content. Peak plasma THC concentrations were higher following THC/CBD equivalent cannabis relative to THC-dominant cannabis, suggesting a possible pharmacokinetic interaction.Conclusions/interpretationCannabis containing equivalent concentrations of CBD and THC appears no less impairing than THC-dominant cannabis, and in some circumstances, CBD may actually exacerbate THC-induced impairment.
Highlights
With the growing worldwide trend towards the decriminalization of recreational and medicinal cannabis use, there has been a renewed focus on the risks associated with driving under the influence of cannabis (Ramaekers 2018; Capler et al 2017)
Sex Race (White/Asian) Age BMI Alcohol intake frequency Age of first cannabis use Days used cannabis in last 28 days Days used cannabis use in last 3 months Years of driving experience Total days driven in last 28 days Typical wait before driving after consuming cannabis (h)
All 14 participants correctly identified the placebo session, and it was commonly reported that less vapor was produced by the placebo cannabis
Summary
With the growing worldwide trend towards the decriminalization of recreational and medicinal cannabis use, there has been a renewed focus on the risks associated with driving under the influence of cannabis (Ramaekers 2018; Capler et al 2017). On-the-road and laboratory studies of driving performance consistently show that cannabis tends to impair driving-related skills and cognitive functions in a dosedependent manner (Veldstra et al 2015; Bosker et al 2012; Lamers and Ramaekers 2001; Downey et al 2013; Hartman et al 2015) These experimental studies of driving performance have typically involved administration of smoked cannabis containing Δ9-tetrahydrocannabinol (THC), or pharmaceutical THC given in a capsule form (e.g., dronabinol) (Veldstra et al 2015; Bosker et al 2012; Lamers and Ramaekers 2001; Downey et al 2013; Hartman et al 2015; Papafotiou et al 2005). It is possible that cannabis containing equivalent CBD and THC will differentially affect driving and cognition relative to THC-dominant cannabis. Aims The present study investigated and compared the effects of THC-dominant and THC/CBD equivalent cannabis on simulated driving and cognitive performance. Conclusions/interpretation Cannabis containing equivalent concentrations of CBD and THC appears no less impairing than THC-dominant cannabis, and in some circumstances, CBD may exacerbate THC-induced impairment
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