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Abstract
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What is the prevalence of cannabis use in randomly selected drivers in traffic?
In roadside surveys, THC is typically the most commonly detected recreational drug after alcohol.
The prevalence of Δ9 tetrahydrocannabinol (THC) positive drivers varies from country to country, depending on the legal status of medical and/or recreational cannabis, the availability of cannabis, prevalence of cannabis use in the general population, traffic laws and their enforcement, and driving culture. A recent systematic review indicates those who use drugs and drive – and in particular, those who use cannabis and drive – are more likely to be younger and male.
What is the prevalence of cannabis use in crash-involved drivers?
Findings from recent studies of crash-involved drivers from different regions are summarized in Table 2. Variation between these studies is explained by cultural and legal factors that influence how often drivers in different countries use drugs or alcohol and by differences in study design. For example, substances are more commonly detected in seriously injured drivers than in drivers involved in minor crashes and different studies use different detection thresholds for reporting THC and/or alcohol.
What is crash risk and how is it measured?
What is the risk of crashing after using cannabis?
Cannabis, when consumed alone, is associated with a modest increase in crash risk at the population level according to most studies which compared the presence versus the absence of cannabis.
How does crash risk vary with THC concentration?
Limited data suggest that risk increases for drivers with whole blood THC ≥ 5ng/mL
How does the crash risk associated with cannabis compare with that of alcohol?
The crash risk associated with alcohol is much higher than cannabis.
What are the major limitations of epidemiological studies? - Failure to measure recent cannabis use or impairment.
- Delays in obtaining blood to measure THC.
- High refusal rates in case-control studies.
30 references
- Difficulty assigning responsibility in responsibility analyses.
Keywords: cannabis impaired driving |