Roadside saliva tests might not be the best way to determine whether someone’s driving is affected by cannabis, new research has found.
Anti-drug-driving programs using saliva-based tests for tetrahydrocannabinol (THC), the active compound in cannabis, are in use by police across the country.
But researchers at the University of Sydney’s Lambert Initiative have found that the levels of THC in a person’s system do not directly correlate to how badly a person is affected by the drug.
The study’s lead author, Danielle McCartney, said unlike alcohol, which has a clear affect on most people the more of it is in their system, THC has a more complex interaction with the human body.
“There are a couple of reasons THC might not directly affect someone, despite being in their system,” Dr McCartney said. “One of those is that there might be different levels of THC in the blood compared to the brain, where it would have an impairing effect.
“Another might be that THC is metabolised into other compounds that are impairing themselves, so they could be having an effect on you also.”
The researchers pooled the results of 28 independent studies to get their results, looking at the effects of both ingested and inhaled THC.
They found that the levels of THC were more indicative of impairment in occasional users compared to regular users, while some people who had only small amounts of THC in their system showed major impairment, and vice versa.
In all jurisdictions there is a zero-tolerance policy to having drugs in your system while driving, with motorists facing fines and even criminal proceedings.
The research has been published in the journal Neuroscience & Biobehavioral Reviews.
Story written by Stuart Layt for Sydney Morning Herald, read the full story here.
