Background & Objective: Delta (9)-tetrahydrocannabinol (THC) is the main psychoactive
compound in cannabis and is frequently identified in blood samples from apprehended drivers suspected
for driving under the influence of drugs. Changing social norms towards cannabis and higher
acceptability towards the drug emphasize the need for in-depth understanding of the acute neurocognitive
and psychomotor effects caused by cannabis and how these effects are correlated to driving
skills and performance.
Method: In this review, PubMed, Cochrane Central, Scopus, Web of Science, Science Direct, EMBASE
and Google Scholar databases were used to identify and select publications up to January 2017
dealing with acute and chronic neurocognitive effects induced by cannabis and ability to drive.
Thirty-six publications were selected for this review. The studies conducted were experimental, using
simulators or on-road studies and brain imaging (structural and functional) to better understand the
acute and chronic effects on cognitive functions comprised in the short and long-term fitness to drive
after cannabis consumption.
Conclusion: In a case-crossover self-report study a significant odds ratio increase was found for driving-
related injury after combined exposure to cannabis and alcohol compared to cannabis alone (OR of
10.9 and 5.8 respectively). Both, experimental and epidemiological studies have revealed that THC affects
negatively both, psychomotor skills and cognitive functions. Studies of the acute effects of cannabis
on driving have shown that drivers under the influence of this substance are impaired. Indeed,
driving under the influence of cannabis doubles or triples the risk of a crash. Specifically, cannabis use
impairs critical-tracking tasks, increases lane weaving, decreases reaction time, and divided attention.