A Higher-Versus-Lower Dose Split Did Not Establish Hazard-Perception Equivalence
Dividing participants into higher and lower THC-dose groups did not reveal a significant hazard-perception interaction. That null comparison was not an equivalence test or a complete dose-response analysis.
The grouping used the sample’s median
The medicinal-oil study divided dose per kilogram into higher and lower categories. Its analysis tested the effects of condition, dose group and their interaction on video hazard-perception response times. None was significant in that analysis.
Dichotomizing dose loses information
A median split places participants with different doses into the same broad category. The result does not estimate a detailed curve across every dose or identify a boundary below which performance is guaranteed. A nonsignificant interaction also does not establish that the true effects are identical across groups.
The finding needs the sample and task
The study involved experienced medicinal users, heterogeneous prescribed oils and a video-based outcome at a selected assessment time. It did not randomize the same people to a series of standardized THC doses. The null comparison should be reported, but it cannot establish a universally safe amount or the absence of effects on other driving demands. A dose-specific claim requires evidence designed to estimate that particular relationship with adequate precision.
Related analysis: the study’s main findings and limitations.
Research cited
Mieran and colleagues. The effects of orally ingested Delta-9-Tetrahydrocannabinol on drivers’ hazard perception and risk-taking behaviours: A within-subjects study of medicinal cannabis users. Psychopharmacology. DOI: 10.1007/s00213-025-06869-w.
