Medical cannabis has ‘negligible’ impact on driving performance – study

A new study has found few changes in driving performance among patients taking medicinal cannabis products. 

Researchers at Swinburne University in Australia examined the effects of cannabis products on simulated driving performance in a group of 40 patients legally prescribed medical cannabis.

The semi-naturalistic study found ‘no notable evidence of driving impairment’ after dosing their prescribed cannabis products. 

Patients were aged between 22 and 80-years-old and all completed a baseline driving assessment prior to their participation in the study. 

At the testing site, they then consumed their typical dose of medical cannabis (either cannabis-based extracts or flowers) before engaging in a number of driving simulator tests. 

Driving performance outcomes including standard deviation of lateral position (SDLP), the standard deviation of speed (SDS), mean speed and steering variability were evaluated using the Forum8 driving simulator at baseline (pre-dosing), two and a half hours and five hours post-dosing.

Participants were also asked about their perceived driving effort after each drive and saliva and blood samples were collected at multiple timepoints and analysed for THC.

READ MORE: What does UK law say about medical cannabis and driving?

The authors state while those taking oils tended to have higher SDLP values, this was ‘stable over time’ and there was ‘no evidence of impairment for either administration route’. 

The lack of changes in speed variability also suggests a ‘modest but sustained stabilisation of vehicle control’, according to the paper and an increase in average speed five hours after consumption among participants is said to reflect a ‘greater accuracy in adhering to the assigned speed limit’.

The authors state: “Critically, no notable evidence of driving impairment (i.e. a significant decline in driving performance metrics within the simulated driving scenario) was observed for either consumption modality, relative to baseline.”

Concentrations of THC were detected in saliva samples up to six hours after consumption. 

The paper concludes:“By focusing on patients consuming prescribed THC-containing products at therapeutic doses, this study provides critical safety and clinically relevant data that is more representative of real-world medical cannabis use and its potential impact on driving performance. 

“Larger and more controlled trials are necessary to validate and confirm these findings in establishing more definitive conclusions regarding road safety.”