The effects of orally ingested Delta-9-Tetrahydrocannabinol on drivers’ hazard perception and risk-taking behaviours: A within-subjects study of medicinal cannabis users

Taren Mieran; Andrew Hill; Mark S Horswill; Mathew Summers; Kayla Stefanidis

doi:10.1007/s00213-025-06869-w

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The effects of orally ingested Delta-9-Tetrahydrocannabinol on drivers’ hazard perception and risk-taking behaviours: A within-subjects study of medicinal cannabis users

Journal article

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The effects of orally ingested Delta-9-Tetrahydrocannabinol on drivers’ hazard perception and risk-taking behaviours: A within-subjects study of medicinal cannabis users

Taren Mieran, Andrew Hill, Mark S Horswill, Mathew Summers and Kayla Stefanidis

Psychopharmacology, Vol.243, pp.651-670

2026

DOI: https://doi.org/10.1007/s00213-025-06869-w

PMID: 40742445

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Abstract

cannabis

delta-9-tetrahydrocannabinol

THC

road safety

hazard perception skill

Medicinal cannabis use is increasing worldwide, yet its impacts on driving safety in frequent users are not clearly understood. A more comprehensive understanding of the effects of THC on driving behaviour in frequent users is needed to guide drug driving policy and evidence-based advice for medicinal cannabis consumers. This study investigated the acute effects of orally ingested THC oil on medicinal cannabis users’: (a) hazard perception skill performance; (b) driving-related risk-taking behaviours (speeding propensity, following distance, gap acceptance); (c) self-perceived hazard perception skill performance; and (d) self-perceptions of driving skills and safety. A within-subjects design was used to compare scores on validated video-based measures of hazard perception skill and risk-taking behaviours, along with self-report measures, between baseline (no THC) and post-consumption. Although participants’ (N = 41) actual hazard perception skill performance did not significantly decline from baseline to post-consumption, their perceived performance did (with no significant correlation between the two in either condition). In the other video-based measures, participants selected significantly slower speeds and longer following distances post-consumption (but gap acceptance behaviour was unchanged). There was no significant change in self-perceptions of driving skills and safety after correction for multiple tests. While there was no evidence that oral ingestion of THC oils by medicinal cannabis users impacted hazard perception skill performance, they were unable to accurately self-assess their performance, regardless of whether they had consumed THC. Further, medicinal cannabis patients engage in compensatory strategies, specifically by reducing their speed and increasing their following distance following the consumption of THC.

Details

Title: The effects of orally ingested Delta-9-Tetrahydrocannabinol on drivers’ hazard perception and risk-taking behaviours: A within-subjects study of medicinal cannabis users
Authors: Taren Mieran - University of the Sunshine Coast, Queensland, Road Safety Research Collaboration
Andrew Hill - The University of Queensland
Mark S Horswill - The University of Queensland
Mathew Summers - University of the Sunshine Coast, Queensland, School of Health - Psychology
Kayla Stefanidis (Corresponding Author) - University of the Sunshine Coast, Queensland, Road Safety Research Collaboration
Publication details: Psychopharmacology, Vol.243, pp.651-670
Publisher: Springer
Date published: 2026
DOI: 10.1007/s00213-025-06869-w
ISSN: 1432-2072
PMID: 40742445
Copyright note: This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
Data Availability: The authors do not have approval to share the data.
Grant note: This research was funded by the Motor Accident Insurance Commission.
Organisation Unit: Road Safety Research Collaboration; Healthy Ageing Research Cluster; School of Health; School of Health - Psychology; School of Law and Society
Language: English
Record Identifier: 991148039502621
Output Type: Journal article

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Web Of Science research areas: Neurosciences; Pharmacology & Pharmacy; Psychiatry

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