U.S. Grapples With How to Gauge Just How High Cannabis Users Are

Impairment tests are becoming big business

Druid App was featured in this article from Bloomberg News written by Tiffany Kary


“Walk a straight line” isn’t going to cut it anymore as police and employers grapple with growing use of marijuana.

Earlier this month, a study in a peer-reviewed journal became the latest sign that there’s a paradigm shift going on in the nascent business of detecting impairment levels. The article, which appeared in Neuropsychopharmacology, showed that an imaging technique can detect cannabis impairment with 76% accuracy. That’s better than the 68% accuracy of field tests that employ traditional law enforcement protocols such as walking a straight line and examining a subject’s pupils.


The technique, called functional near-infrared spectroscopy, measures changes in the prefrontal cortex of the brain. It shows that impaired brains look different than non-impaired brains in a way that doesn’t necessarily correlate with the amount of THC in a person’s system. THC detection in saliva or on the breath has so far been the main focus of tests. The study was carried out on 169 people at Massachusetts General Hospital, which is part of Harvard Medical School.

The study is a big deal for the cannabis industry, since the lack of a clear test to gauge intoxication has become a stumbling block for federal legalization. Though links between marijuana and accidents have been hard to draw due to factors such as the frequent mixing of alcohol with drugs, the study estimates that THC, which is the psychoactive ingredient in cannabis, at least doubles the risk of fatal motor vehicle crashes.


The research arm of the U.S. Department of Justice has acknowledged that field sobriety tests and THC levels are unreliable measures of marijuana intoxication. Methods like the “one-leg stand” and “walk and turn” weren’t affected by marijuana highs, and some people had poor functions even when their THC levels were low.


States’ efforts

States have forged ahead nevertheless. According to New Frontier Data, at least five states have adopted protocols that set a legal limit for driving based on the level of THC in the body. That has sparked a lot of interest in tests that can actually measure that level — a scientific challenge unto itself.


“Everybody wants a cannabis breathalyzer — something like what we have for alcohol where you breathe into a device and it tells a THC level and whether that means you’re impaired or not,” said Jodi Gilman, an associate professor in psychiatry at Harvard Medical School and lead author of the imaging study. “But that’s not how it works for cannabis, we need a new paradigm.”

Companies have been trying to crack the stoned-test for a while. Hound Labs, which makes a marijuana breathalyzer, said in September it had raised $20 million to scale its product. Cannabix Technologies Inc. recently reported it had made headway creating a more portable device, while Lifeloc Technologies Inc. said it was finalizing the platform for a rapid marijuana breathalyzer that could be used for roadside testing.


There are concerns, however, that tests based on THC levels may be unfair to those who have it in their system but aren’t actually impaired. This can be the case for some who consumed cannabis days ago, or with frequent users who’ve built up a tolerance — who may use it for medical reasons.

“You wouldn’t want to penalize that person,” Gilman told me. “What this technology will do is differentiate impaired from not-impaired, which is different than distinguishing cannabis from no-cannabis.”


Impairment app

One company that uses a similar approach is Cambridge, Massachusetts-based Impairment Science, which has an app called Druid to measure response times and motor skills through a series of tests on a screen. The methods let the app gauge impairment, regardless of whether the cause was alcohol, marijuana, or something else. The company aims to raise as much as $1.2 million in seed funding, according to Chief Executive Officer Robert Schiller.


Druid is being pitched to construction companies, and Impairment Science recently struck a deal with Anheuser-Busch InBev SA’s Grupo Modelo, which will promote the app in an effort to reduced drunk driving in the Mexican state of Zacatecas. Schiller said the company plans to announce more corporate partnerships in the near future.


Still, there are no easy solutions. Druid’s app requires that people take the test more than once in order to gauge impairment compared to a baseline score. The company is researching a product where tests could be one-offs, which would appeal to law enforcement.


The method used by Gilman also has its limitations. It relies on an imaging device from NirX Medical Technologies, which still costs around $40,000. For better or worse, the techniques used by Gilman’s study and Druid’s app will also pick up forms of impairment that arise from issues other than marijuana, such as fatigue, illness or chronic medical conditions. That could be a good thing for public safety — especially at a time where perception-altering drugs like psilocybin are on the rise, and other drugs like opiates also create risks in driving and high-risk industries — but it could create other problems.


It’s not hard to envision a future where people could be taken aside and wired up for a quick scan that checks their brain for telltale signs of impairment. Then comes the real work: Employers, insurers and police will have to figure out what to do with the information.




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