New research from the Lambert Initiative for Cannabinoid Therapeutics shows that cannabis impairment lasts up to 10 hours – shining a critical light on Australia’s current cannabis driving laws.
The Lambert Initiative is one of Australia’s premier research bodies for cannabis. It is a part of the University of Sydney. Recently, Dr. Danielle McCartney and researchers from the initiative published a new study in the journal Neuroscience & Biobehavioral Reviews.
The study carried out a meta-analysis of 80 scientific studies conducted within the last twenty years, focusing on cannabis and impairment. As the psychoactive components of cannabis (like THC) affect the brain, research has previously shown that cannabis reduces a person’s reaction times, working memory and attention span after use. While this gives it a calming effect, it also impairs driving performance and a person’s ability to operate heavy machinery.
In the analysis of previous studies, researchers were able to pinpoint a “window of impairment” lasting 3 to 10 hours after cannabis consumption. They also found that people who inhale 20mg of THC recover “most” driving-related skills within 5 hours and “almost all” driving-related skills within 7 hours. The “typical” duration of impairment lasts only four hours.
The study also found that the effects of cannabis impairment are greater when cannabis is taken orally (like through cannabis oil, edibles, sprays, and capsules) and in casual cannabis users. To researchers, this says that regular users build up a tolerance to cannabis.
As this study pinpoints how long cannabis impairment actually lasts, it has huge implications for drug-driving laws and Australia and globally. Currently, Australian police assess cannabis-impaired drivers using a similar model to drink-driving, where they test drivers for the presence of THC in blood and saliva.
However, unlike alcohol, the presence of THC doesn’t necessarily indicate someone is impaired. According to previous research, THC can stay in your body for weeks after consumption, even though the “high” has subsided.
This is “manifestly unjust”, according to Professor Iain McGregor – the academic director of the Lambert Initiative.
Laws should be about safety on the roads, not arbitrary punishment. Given that cannabis is legal in an increasing number of jurisdictions, we need an evidence-based approach to drug-driving laws.
This is the second major study that has shined a critical light on Australia’s cannabis driving laws after another University of Sydney study found that THC in medical cannabis only affects driving for up to four hours.