Study: THC Levels Don’t Accurately Signify Degree of Impairment

The National Institute of Justice argues the amount of THC intake and the manner in which it was consumed isn't an accurate measure of intoxication.

Police man giving a breathalyzer

A new study published by the National Institute of Justice finds that field sobriety tests used to determine whether someone is driving while impaired by the use of marijuana are not accurate. 

Right now, there are plenty of tests and devices on the market that claim to be able to measure the presence of THC. Some of those have come under fire recently.

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Field Tests Today 

With laws changing constantly from state to state, and even federal rules relaxing on certain cannabinoids, police are having a hard time keeping up. Right now, field tests are simply not reliable. Even drug-sniffing dogs alert on both CBD and THC.

In 2019, a news team with NCB4 in Washington D.C. found several cases across Virginia where a police field test checking for marijuana couldn’t distinguish between THC and CBD. That’s because hemp-derived CBD products are legally permitted to have up to 0.3% of THC under federal law, thanks to the 2018 Farm Bill

A kit designed in Switzerland says it’s able to tell whether THC goes above the legal limit. But the mass distributor of the test in America says the test isn’t perfect, and putting in too much product can lead to inconclusive results.

A woman at the Virginia Department of Forensic Science is working on a test that can measure THC levels of marijuana and CBD, but it only works for oils, not other products. 

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A new marijuana breathalyzer claims to be a DUI game changer. It was developed by a research team out of Pittsburgh and says it uses carbon nanotubes that THC molecules in breath will bind to, changing their electrical properties. The team says those sensors can detect THC levels better than a mass spectrometer. The problem is, there’s no standard of impairment like there is for blood-alcohol level.

The New Study

A research study funded by a grant to RTI International found that even though there may be some new tests that can determine the exact level of THC in one’s biofluid, that is still not a reliable indicator of marijuana intoxication. Even when study participants had low levels of THC in their blood, urine, and oral fluid, they still had significantly decreased cognitive and psychomotor functioning, the researchers noticed. 

The researchers set up six different double-blind dosing sessions spaced at least a week apart, during which study participants either ate cannabis brownies containing 0 mg, 10 mg, or 25 mg of THC, or inhaled vapor containing 0 mg, 5 mg, or 20 mg of THC. 

Before and after THC dosing, the study participants went through five different common impairment tests. One of those was the standardized field sobriety test that law enforcement officers use to detect alcohol impairment, such as standing on one leg, walking and turning, or tracking eyes for pupillary response. That turned out to not work as a test for marijuana impairment. For the other tests, the researchers said the participants’ psychomotor and cognitive abilities got worse with any amount of weed other than the 5 mg vaped dose. 

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People who ate edibles said they felt like they peaked after 3-5 hours, and people who vaped the weed felt their peak in the 0-1 hour range. As far as cognitive and psychomotor effects, vaped doses over 5 mg were at their highest in the 0-2 hour range; people who had oral THC doses started displaying cognitive and psychomotor impacts after one hour, and that peaked 5 hours after consumption. 

Here’s the kicker: the researchers sent biofluid samples collected before dosing and from each hour after dosing to be analyzed in forensic toxicology labs. Here’s what they found: 

“Results from the toxicology tests showed that the levels of all three targeted cannabis components (THC, cannabidiol, and cannabinol) in blood, urine, and oral fluid did not correlate with cognitive or psychomotor impairment measures for oral or vaporized cannabis administration.”

The researchers explained, many of the study participants showed decreased psychomotor and cognitive functioning even when their blood, urine, and oral fluid contained only very low levels of THC. That makes it hard to determine impairment based on the results of those tests alone.

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“The RTI researchers hope their work will inform policy for cannabis impairment and driving under the influence of drugs and help establish scientifically-based thresholds for marijuana intoxication,” the study concludes.

False Arrests from Confusing Laws and Inaccurate Testing 

There are stories of false arrests for confusion over impairment or the difference between CBD and marijuana all over the country. The problems don’t center around impairment alone.

At least three truckers and two security guards hauling legal, state-certified hemp across state lines have been stopped and arrested by police who were unable to tell the hemp apart from marijuana flower. With thousands of pounds of the product in each load, those transporters are hit with felony drug trafficking charges. An attorney in Colorado says he has about half a dozen clients with similar plights. A Marine veteran who served in Afghanistan and Iraq is facing 18-years-to-life in Oklahoma after providing security for a state-certified load of hemp from Kentucky. Those charges were eventually dropped.

In Scottsbluff, Nebraska, a mother-son team operating a CBD shop had barely had their store open for one day before police raided the place.

People at the Dallas Fort Worth International Airport have been jailed on felony drug possession charges for having bottles of CBD. A port director for U.S. Customs and Border Patrol at DFW says the number of people moving through the airport with CBD has skyrocketed. Arrests there have ranged from a 71-year-old woman jailed after authorities found a vial in her bag that she said was CBD oil that she uses for medicinal properties like pain relief, to a 22-year-old college student who officers caught with a brown bottle labeled “hemp CBD” during a random bag check.

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The arrests have even permeated the Happiest Place on Earth. A 69-year-old great-grandmother was detained for 15 hours when authorities at Disney World in Orlando found a bottle of CBD oil that she says her doctor in North Carolina recommended for pain and stiffness from arthritis. Body camera video of the incident shows an officer saying over the radio, “She had CBD in there.” She even gave the Orange County Sheriff’s Office a doctor’s note and was eventually let go. She and famous attorney Ben Crump sued both the Walt Disney Company and the Orange County Sheriff’s Office in response.

FDA Viewpoint

When it comes to cases like these, the Food and Drug Administration is fairly hands-off. Although the federal government has come to accept CBD, there is only one FDA-approved CBD product, which is used to treat seizures. Right now, it’s still illegal to market CBD as a dietary supplement, and companies are not allowed to add the product to foodstuffs. In some regards, the Administration seems fairly supportive of CBD, stating,

“There is a significant interest in the development of therapies and other consumer products derived from cannabis and its components, including cannabidiol (CBD). FDA recognizes the potential opportunities that cannabis or cannabis-derived compounds may offer and acknowledges the significant interest in these possibilities.”

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But the FDA is also cautious, citing potential side effects like livery injury and slowed brain activity. The Administration also wants to learn more about how different methods of consumption like vaping, topicals, smoking, or oral consumption might impact intake. RTI’s study tested that, and found the greatest difference in impairment to be simply the length of time between when someone experiences peak effects if they vape or if they take in THC orally. 

Study: THC Levels Don’t Accurately Signify Degree of Impairment was last modified: by