As medical (and recreational) cannabis becomes more widely available, the potential impacts on our roads are becoming a more pressing issue.
In some places, patients using medical cannabis (regardless of its type or dosage) are outright banned from driving, or not permitted to drive X hours after taking medications. Is this really necessary? It may well be – but it also depends on the type and dosage.
A recently published study compared the effects of tetrahydrocannabinol (THC)-dominant and THC/cannabidiol (CBD) equivalent cannabis on simulated driving and cognitive performance. The study was carried out by researchers from the Lambert Initiative for Cannabinoid Therapeutics at the University of Sydney.
For the testing, the following was delivered via vaporisation: 125 mg THC-dominant (11% THC; 1% CBD), THC/CBD equivalent (11% THC, 11% CBD), or placebo ( 1% THC/CBD) cannabis.
The researchers found both THC-dominant and THC/CBD equivalent types increased lane weaving during a car-following task, but had little effect on other driving performance measures. However, performance was impaired on the Digit Symbol Substitution Task (DSST), Divided Attention Task (DAT) and Paced Auditory Serial Addition Task (PASAT), with worse results on the latter two tasks with THC/CBD equivalent cannabis.
This is particularly interesting as CBD has often been claimed as reducing some of the impairment caused by THC.
“Cannabis 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,” states the study.
Cannabis effects on driving are not nearly as predictable as those