Cannabis and Its Effects on Driving and Cognitive Function

Abstract

Prior research shows that acute cannabis intoxication can impair driving ability and related cognitive functions, yet there is considerable uncertainly around the magnitude and duration of this impairment. The extant cannabis and driving literature has focused predominantly on Δ9‐tetrahydrocannabinol (THC), the primary psychoactive component of cannabis. However, with changing cannabis laws and a rapidly expanding commercial cannabis industry, many consumers now have access to a vast range of botanical cannabis types (strains) and products (e.g. oils; edibles) that were previously unavailable. Many of these products contain high levels of cannabidiol (CBD), a non-intoxicating component of cannabis that shows emerging therapeutic potential in treating a wide range of clinical conditions. There is some evidence that CBD and THC may interact pharmacokinetically or pharmacodynamically, including suggestions that CBD may attenuate certain THC effects, such as anxiety and cognitive impairment. The implications of this interaction in relation to cannabis-induced driving impairment are unknown. This thesis centers around a series of clinical investigations designed to address these unknowns and build on existing knowledge around cannabis’ effects on driving. It aims to (1) quantify the magnitude and duration of driving and cognitive impairment produced by THC, (2) establish whether CBD attenuates this impairment, and (3) determine whether CBD impacts driving or cognitive function when administered alone. It also explores attitudes toward DUIC among a sample of Australian medical cannabis users and considers the effectiveness of point-of-collection testing (POCT) and per se limits as approaches to detecting cannabis-impaired driving. It is hoped that the work contained in this thesis will advance our understanding of how cannabis impacts driving and help to guide future evidence-based policy to manage the associated risks.