Effects of prescribed medical cannabis and alcohol on real-world driving performance (CAN-TRACK): a study protocol for a two-phase trial

TL;DR

This study aims to assess how prescribed medical cannabis and alcohol affect real-world driving performance to help shape road safety policies.

Contribution

The study introduces a novel two-phase trial to evaluate the impact of prescribed medical cannabis and alcohol on driving performance.

Findings

The trial will measure changes in lateral vehicular control after cannabis or alcohol consumption.

Cognitive and subjective assessments will be used alongside biological samples to evaluate impairment.

Results may inform policies on driving under the influence of medical cannabis.

Abstract

Medical cannabis is now commonly prescribed for a range of chronic health conditions. Many medical cannabis products contain delta-9-tetrahydrocannabinol (THC), the intoxicating component in cannabis, though it is unclear whether these products produce impairment when used as prescribed and at therapeutic doses. With current Australian laws prohibiting driving with any amount of THC in one’s system, this trial aims to generate novel data on the impact of prescribed medical cannabis on real-world driving performance to inform road safety policy.

This is a two-phase trial, with the first phase being a semi-naturalistic cohort study involving 72 patients with physician-diagnosed chronic pain, anxiety, or insomnia (n = 24 per group) who will complete repeated on-track driving assessments before and after consuming a standard dose of their medical cannabis prescription. The second phase is a randomised, placebo-controlled, double-blind, and crossover study involving 24 healthy participants who will complete the same repeated on-track driving assessments before and after consuming either alcohol (0.05% blood alcohol concentration) or placebo. Participants in both phases will also complete repeated cognitive assessments and assessments of subjective state and provide biological samples for analysis of cannabinoid (phase 1) and alcohol (phase 2) concentrations. The primary outcome measure is lateral vehicular control. Data will be analysed using a series of mixed-effect and generalised linear mixed models to assess changes in outcome measures over time.

ACTRN 17/09/2024 for 12624001118594 and 24/09/2024 for 12624001163594.

The online version contains supplementary material available at 10.1186/s13063-026-09512-x.

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