Studying weed behind the wheel

CAMH researching combined effects of pot, booze on young drivers

No one knows what kinds of havoc Canada’s freshly open cannabis laws might bring to the country’s roadways. But researchers at Toronto’s Centre for Addiction and Mental Health are trying to find out.

In particular, CAMH scientists are studying the combined effects of cannabis and alcohol on young drivers — and the ways in which the two intoxicants might work together to impair them behind the wheel.

“The effects of alcohol on driving behaviour are really well known,” noted centre scientist Christine Wickens, a road safety expert.

It’s well known, for example, that collision risks surge exponentially with upped alcohol intakes, and that weaving, speeds, reaction times and risk-taking all increase with drinking, she said. With cannabis — and especially its psychoactive THC component — the effects on driving are more uncertain.

“Arguably a reduction in speed is probably the most consistent effect of cannabis on driving,” said Wickens. “But studies have also shown a number of other effects as well, including impaired lane control, reduced dual-task control … and increased reaction times.”

While some effects, like driv- ing speeds and following distances, are altered differently under the two influences separately, there is good evidence that together pot and booze could compound road risks, Wickens said.

“We have some indication that having alcohol and cannabis on board is worse than having either one of those substances alone,” she said. “But what that actually looks like in terms of impacts to driving performance, that’s really still not very well understood.”

So the CAMH team is recruiting some 50 study subjects age 19 to 25, giving them booze and pot cocktails and putting them behind the wheel of an on-site driving simulator.

Study participants — about a dozen of whom are already being tested — will come to CAMH at least four times each. With each visit they’ll be administered different alcohol and THC combinations.

“What is the profile of that driver who is using both substances?” Wickens said. “We know that their collision risk is going to be much higher, but why is that? Is it increased weaving, is it a change in speed? What is it we’re seeing on the road when somebody has both these substances?” The answers the CAMH studies provide will be invaluable in understanding how to make roadways — here and across the globe — safer, said MADD Canada CEO Andrew Murie.

“It’s absolutely critical,” Murie said. “It’s pretty accepted that when you combine the two it’s worse than if they’re used separately, but we don’t know how much worse and we need to know that and we need to get that information out to people.”

And those people will include the hundreds of millions in multiple jurisdictions around the world currently considering cannabis legalization, Murie said.

“It’s pretty accepted that when you combine the two it’s worse than if they’re used separately.” ANDREW MURIE MADD CANADA CEO

Wickens adds that road enforcement could be improved when patrolling officers know what to look for.

“Being able to detect or to perceive how the driver is behaving behind the wheel will help (police) understand what substances that individual may be using,” she said.

A principal researcher on the study, Martin said it will also look at the body chemistry of alcohol and THC together to give a better idea of what’s in play biologically.

Most importantly, however, the groundbreaking CAMH study — which will run at least another year — is the first to engage subjects in real life-anddeath simulations, Martin said.

“There’s been a lot of epidemi- ological research where we’ve looked at crash data and crash statistics, but not a whole lot that has looked at it in the lab using these advanced simulation techniques,” she said.

Past pot and booze studies have tended to look at individual reactions — such as hand-eye co-ordination — in isolation, Martin said.

“Early studies that looked at a single cognitive task or a single psycho-motor ability were really looking at one very small component of driving,” she said.

“The simulator allows us to look at all of those things happening at once. You’re looking ahead and you’re previewing your environment and you’re making decisions and you’re physically moving your steering wheel.”

Wickens said the study is concentrating on young drivers because they — typically being the most novice of drinkers, tokers and drivers — likely represent the largest road risks.

The ability of scientists to legally employ the product in their work has been touted as a boost for cannabis research in this country — offering scientists here the chance for world leadership in the field. But Wickens said officials still made her team jump through onerous regulatory hoops before allowing the study proceed.

“There are still a lot of regulatory oversights in place,” she said. “It’s not much easier, let’s put it that way.”