A new study from the University of British Columbia (UBC) is suggesting that Canada’s cannabis-impaired driving penalties may be too strict.
That’s after researchers found no link between low levels of THC, the psychoactive chemical in pot, and car crashes.
The study, recently published in the journal Addiction, also looked at the impact of other illegal drugs and alcohol on collisions.
Under Canada’s drug-impaired driving laws, drivers found to have blood THC levels of between two and five nanograms per millilitre are liable for a fine of up to $1,000, while drivers with over five nanograms face a minimum $1,000 fine and up to 10 years in prison for a first offence.
THC levels in the blood spike quickly after smoking cannabis but drop to two nanograms per millilitre within four hours of smoking. Edible products drop similarly about eight hours after ingesting THC, according to UBC researchers.
The UBC study analyzed blood samples from more than 3,000 drivers who were treated in B.C. trauma centres between 2010 and 2016. It looked at accident reports for more than 2,300 of those crashes and included 1,178 of those in which the driver was deemed responsible for the crash in its final analysis.
In analyzing blood samples from those drivers, researchers found no increased risk of crashes when THC levels were below five nanograms per millilitre. It said there may be an increased risk of crashes above that level but that just 20 of 1,825 samples tested had THC greater than that amount.
“At blood levels of less than five nanograms/ml, THC does not appear to be associated with an increased risk of crashing,” said Dr. Jeffrey Brubacher, an associate professor at UBC’s emergency medicine department and lead investigator in a five-year study looking at cannabis and crashes.
“That’s significant because the new impaired driving laws do include penalties for drivers with THC levels between two and five nanograms/ml, suggesting that the laws may be too strict.”
In contrast to THC, researchers found recreational drugs such as cocaine, amphetamines and heroin increased the risk of a crash by 82 per cent.
Sedating medications such as antihistamines, benzodiazepines, other hypnotics and antidepressants were also found to boost crash risk by 45 per cent.
Alcohol was found to have the highest association with crash risk, with drivers showing a blood-alcohol content over 0.08 six times more likely to crash compared to non-drinkers.