Can a game-based impairment app tell if you’re stoned? Not always, we found

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Robyn, a 48-year-old Toronto woman, says she certainly felt impaired.

After not consuming any cannabis between the 1990s and this month, she took three 2.5-milligram THC capsules and gave them time to take effect. In due course, they did.

“I really noticed that my brain was only running on one track. I could do one task,” she says. “Normally, I have two or three tracks that keep going in my head simultaneously.

“It was, OK, get off the bus, look left for traffic, now look right for traffic, now look left again because you’ve forgotten what you saw when you looked before. It was very much a one-track kind of thing. I really had to focus to keep moving through life.”

Then she played the Druid impairment app, a video game-based test designed to test intoxication. Users (who set a personal base level when not impaired) have to stand as still as possible on one foot, chase a shape on the screen while estimating 60 seconds and respond differently to circles and squares. The higher the score, the higher the level of impairment.

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“People say: ‘That’s a really challenging app,'” explains its inventor, University of Massachusetts psychology professor Michael Milburn. “I say: ’So is driving.’ You have to have all your wits about you when you’re driving. You have to be able to perform divided-attention tasks.”

But Robyn says she got the same score (on four separate occasions) completely sober, after half a bottle of wine, after 2.5 milligrams of THC and after 7.5 milligrams of THC.

She scored consistently around 37; Milburn says a 55 would roughly indicate a 0.08 blood-alcohol concentration, or its equivalent.

In some ways, she says she found the test went more smoothly with some cannabis.

“I tried it at an hour and a half and two hours, and it was the same result. I found it easier when I was impaired because I didn’t have those brain tracks going off in different directions. It’s a fairly boring task: just sit there and poke the circles or the squares for a minute,” she says.

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Robyn didn’t want to be further identified because of concerns about the U.S. border.

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She also found the balance test easier when THC dulled pain from arthritis in her foot.

“I thought, ‘That hurts, but I don’t really care.’ I didn’t have the urge to wiggle around and get off it. That made me more steady and more settled, so I found it easier,” she says.

Milburn says he’s aware of individual factors like this.

“There’s a complex pattern of how medical issues interact with Druid,” he says. “We may need to introduce modifications for it as we go forward. I have one guy who managed my website for quite a while who has epileptic seizures, just a kind of an ongoing tremor, and his Druid score improves (with cannabis).”

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“It depends on your own brain and your own body,” Robyn says. “It might work well for somebody else.”

Regardless of the test results, she says she wouldn’t have considered driving.

“That single-track thinking would really be a deterrent. You need to pay attention to so many different things. You can’t forget about what you’re doing because you’ve suddenly been distracted by a squirrel in the trees. I don’t think it would be safe at all.”

Testing at Massachusetts police training facilities showed a clear relationship between Druid scores and alcohol intoxication, with scores moving up along with blood-alcohol levels.

U.S. federal prohibition of marijuana has made it much harder to test on cannabis, though Johns Hopkins University in Baltimore recently got a grant in part to study Druid’s ability to detect cannabis impairment.

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While the results won’t be formally published until the fall, Milburn says the Johns Hopkins experiments showed a consistent relationship between THC volunteers consumed and their scores.

“(The researcher) had 20 people do Druid six times each for 120 different Druid measurements that showed that pattern. I would have more confidence in his results than I would in an anecdotal report by someone who’s not doing it under careful, controlled conditions,” he says.

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Video game-based testing has limited use in law enforcement, since police have no way of knowing what a given driver’s base score is. But it has been adopted by some industrial workplaces in the U.S., which see it as more objective and less intrusive than urine-based drug tests.

READ MORE: Are video games, not urine tests, the key to addressing pot in the workplace?

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“I didn’t design Druid so cops could bust stoned drivers,” Milburn says. “I wanted to stop the stoned drivers from getting in the car in the first place.

“Druid doesn’t tell people that they’re safe to drive. It says if there’s evidence of impairment. We say clearly, multiple times, that if you’re using drugs, your decision to drive is on you. We state that pretty clearly, that the decision is up to the individual.”

(Druid appears to respond to fatigue. A reporter testing the app first thing on a recent Monday morning was ruled “mildly impaired.”)

The app has been downloaded about 12,000 times, Milburn says. Most users are in the U.S., with Canada in second place and the U.K. and Europe a distant third.

Regardless, Robyn calls the app an “excellent idea.”

“Maybe there needs to be a wider variety of tasks, and you pick the ones that work best for you,” she says.

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