Most street cannabis contains large quantities of THC, the chemical in cannabis that gets people ‘high’, but there is increasing use of medicinal products that also contain CBD, a non-intoxicating cannabinoid with promising therapeutically potential. It has often been proposed that administering CBD may reduce some of the impairment caused by THC. To test this, we compared the effects of standard THC-dominant cannabis with cannabis containing equivalent amounts of THC and CBD and placebo on simulated driving and cognitive performance. Contrary to prediction, the study found that the addition of CBD to THC did not reduce feelings of intoxication, nor did it lessen impairment on measures of driving ability and cognitive performance. A follow-up study involving on-road driving is now underway at Maastricht University with the support of the Lambert Initiative for Cannabinoid Therapeutics at the University of Sydney.
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