Cannabis legalization has increased access to cannabis products, which has, in turn, led to a growing concern over how cannabis may impact driving. Epidemiological research suggests that the risk of motor vehicle collisions increases following cannabis use.
Current legal thresholds for blood tetrahydrocannabinol (THC) while driving are largely based on evidence from smoked cannabis. However, research indicates that consuming edibles produces different effects than smoking, such as lower blood THC levels, a longer time to reach peak levels of THC, and longer-lasting effects. Understanding more about how cannabis edibles impact driving is key for informing public policy around cannabis use.
In the present study, researchers recruited 22 participants with an average age of 47 years old. Each had a valid driver’s license, and were asked to drive a driving simulator in two conditions: after ingesting their preferred legally purchased cannabis edible and after consuming a control candy without any THC or cannabidiol (CBD). Cannabis edibles contained an average of 7.3mg of THC. The researchers assessed particpants' subjective experience and took blood samples to measure levels of THC and metabolites alongside CBD.
Ultimately, cannabis edibles were linked to a decrease in mean speed two hours after consumption but not after 4 and 6 hours. There were no changes in standard deviation of weaving, maximum speed, or reaction time between cannabis and control conditions.
While THC levels in the cannabis condition were significantly increased relative to the control condition, they remained relatively low at around 2.8 ng/mL two hours after consumption. Driving impairment was not correlated with blood levels of THC. The researchers noted, however, that participants’ subjective experience was altered for 7 hours, and that they felt less willing to drive for up to six hours. This, noted the researchers, suggests that cannabis edibles had intoxicating effects.
“This is the first study of the impact of cannabis edibles on simulated driving. Edibles were intoxicating as revealed by the results of subjective assessments (VAS), and there was some impact on driving.” wrote the researchers in their paper.
“Legal thresholds of blood THC at the roadside are largely based on research utilizing the smoked route of administration and the present study suggests that the edibles route may be different in important ways,” they concluded.
Sources: Journal of Cannabis Research