Introduction: A groundbreaking study conducted in Ontario has shed light on the effects of edible cannabis on simulated driving and blood THC levels. Unlike previous research, which primarily focused on smoked or vaped cannabis, this study specifically examined the impact of cannabis edibles. The findings challenge conventional wisdom and provide valuable insights for policymakers, law enforcement, and cannabis users alike.
Driving Impairment and Blood THC: The Study
Researchers recruited 22 participants (16 male and 6 female) who met specific criteria: they held valid Ontario driver’s licenses, had consumed cannabis edibles at least once in the past six months, and drove at least once a month. The participants’ age ranged from 19 to 79 years. Before the study, they refrained from using cannabis for 72 hours and avoided other drugs or alcohol for 12 hours.
The study involved three independent, pre-programmed driving scenarios:
- A two-lane rural highway test
- A “potentially frustrating event” to assess speed
- A lateral control test on a four-lane highway to evaluate reaction time
On average, participants ingested approximately 7.3 mg of THC (with 2.14 mg of CBD). Interestingly, some chose the maximum allowable dose of 10 mg THC, while others opted for edibles containing 5 mg THC or less. Blood samples were collected two hours after consumption.
Surprising Results: No Correlation Between Blood THC and Driving Impairment
Contrary to expectations, the study found no direct relationship between blood THC levels and driving impairment. Here are the key findings:
- Speed Reduction at Two Hours: Participants who consumed cannabis edibles experienced a decrease in mean speed at the two-hour mark. However, this effect did not persist at the four- or six-hour marks.
- Effects Beyond Two Hours: Some participants reported lingering effects up to six hours after ingestion, affecting their ability and willingness to drive. This extended duration surprised researchers.
- No Swerving or Reaction Time Changes: Unlike previous studies involving smoked or vaped cannabis, this study did not observe increased swerving or decreased reaction time. The relatively low THC dose or limitations of the driving simulator may explain this discrepancy.
- Blood THC Levels: After two hours, blood THC levels averaged around 2.8 ng/mL. Although blood THC increased significantly after consuming edibles, the mean increase was lower than that seen with smoked cannabis.
- Implications for Detection of Impaired Driving: The study suggests that blood THC may not be as useful for detecting impairment after consuming edibles as it is for the smoked route. Linear correlations between blood THC and driving impairment were absent.
This study challenges existing assumptions about cannabis edibles and driving impairment. Policymakers and law enforcement agencies should consider these findings when developing regulations and roadside testing protocols. As cannabis legalization continues, understanding the nuances of impairment becomes crucial for public safety.
