Acute and residual effects of smoked cannabis: Impact on driving speed and lateral control, heart rate and self-reported drug effects
Brands, B., Mann, R. E., Wickens, C. M., Sproule, B., Stoduto, G., Sayer, G. S., ... & George, T. P. (2019). Acute and residual effects of smoked cannabis: Impact on driving speed and lateral control, heart rate, and self-reported drug effects. Drug and alcohol dependence, 205, 107641.
With increasing availability of cannabis products and its decriminalized status in many states, understanding its acute and residual effects on driving is important in promoting public health and in guiding law enforcement with implementations of legal limits. In this study, 96 participants were randomly assigned to placebo, low tetrahydrocannabinol (THC) or high THC groups. Measures including speed, lane control, heart rate, and subjective drug effects were obtained at 30 minutes, 24-, and 48hours after exposure to cannabis. Results showed group differences in speed 30 minutes after exposure but not at 24 or 48 hours. More specifically, individuals in the high THC group drove significantly slower than those in the placebo group but the low THC group did not vary from either the high THC group or the placebo group while completing the single task driving test. Interestingly, when distraction is added such as counting backwards while driving (dual task driving test) individuals in both high and low THC group significantly drove slower than those in the placebo group. On analyzing the results of lateral control (tendency to swerve) a significant group difference was observed at 48 hours but not at 24 hours or 30 minutes. The combined results of this study indicate that the acute effects of smoked marijuana correlates with driving slowly especially when a distraction is present. Although the results relating to swerving was inconclusive, it may be beneficial to investigate as to why lane control is difficult to achieve at 48 hours after use but not acutely or 24 hours post exposure.View This Research