Queensland, Australia: Patients who consume oral doses of THC drive at slower speeds and engage in other compensatory behaviors, according to driving simulator data published in the journal Psychopharmacology.
Australian researchers assessed subjects’ simulated driving performance prior to and 90 minutes after their ad libitum consumption of prescribed THC oil extracts. (Australian physicians may prescribe cannabis products to patients unresponsive to conventional prescription treatments.) On average, study subjects consumed 11 mg of THC prior to driving.
Similar to the results of prior studies, subjects engaged in compensatory driving behaviors – such as driving at slower speeds and increasing the distance between their vehicle and the vehicles in front of them – following THC dosing. Few other changes in participants’ baseline performance were identified, leading investigators to presume that patients likely become tolerant to THC’s potential effects on cognitive and psychomotor performance.
“Our results align with a growing body of evidence demonstrating that chronic THC use can mitigate the acute effects of the substance on driving performance and driving-related cognitive functions,” researchers reported.
The study’s authors concluded: “Taken together, our findings suggest that … medicinal cannabis users may … be more inclined to compensate for cannabis impairment through alterations in speed and following distance. … Future research is needed to further investigate the effects of THC on these driving-related skills and behaviors using a wider range of doses and administration methods, with populations of varying tolerance levels.”
The study’s findings are consistent with those of several others, determining that daily cannabis consumers, and patients especially, exhibit tolerance to many of cannabis’ psychomotor-influencing effects. According to the findings of a literature review published in the Journal of the German Medical Association, “Patients who take cannabinoids at a constant dosage over an extensive period of time often develop tolerance to the impairment of psychomotor performance, so that they can drive vehicles safely.”
Full text of the study, “The effects of orally ingested delta-9-tetrahydrocannabinol on drivers’ hazard perception and risk-taking behaviors: A within-subjects study of medicinal cannabis users,” appears in Psychopharmacology. Additional information is available in the NORML Fact Sheet, ‘Marijuana and Psychomotor Performance.’