Driving Under the Influence(s)
Researchers assess impact of cannabis and alcohol – alone and in combination – on driving
Cannabis is the most commonly encountered non-alcohol drug in DUI cases, but how much does it impair driving and what happens when alcohol is added to the mix?
By assessing blood, oral fluid (OF), and breath samples of participants before and after driving impaired, researchers were able to assess the impact of cannabis and alcohol – alone and in combination – using a number of measures, including lane weave (standard deviations of lateral position, SDLP), lane departures per minute, and maximum lateral acceleration – thankfully, using a driving simulator.
The main take home: i) the effects of cannabis and alcohol on SDLP were additive rather than synergistic; 5 μg/L THC + 0.05 g/210 L alcohol showed similar SDLP to 0.08 g/210 L alcohol alone, ii) blood THC ≥8.2 μg/L increased SDLP to similar levels as notably-impairing alcohol concentrations. Interestingly, only alcohol increased maximum lateral acceleration and the less-sensitive lane departures/min parameters.
What else did we learn? i) SDLP appears to be a sensitive cannabis-related lateral control impairment measure, and ii) OF effectively documented cannabis exposure, but with more variable THC concentrations than paired blood samples.
