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  • Writer's pictureAshley Slimak

Study Finds No Increased Crash Risk with Low Levels of THC

Marijuana and driving
Evidence suggests that cannabis use can result in intoxicating effects that might impair driving.

Impaired drivers are a hazard to themselves and others. But what qualifies as impaired driving? When it comes to cannabis, the level of THC in your bodily fluids may be deceiving.

According to Arkansas law, “intoxication includes being influenced by the ingestion of a controlled substance to such a degree that the driver’s reactions, motor skills, and judgments are substantially altered.”

Evidence suggests that cannabis use can result in intoxicating effects that might impair driving. When you use marijuana, the psychoactive compound THC inhibits memory, motor skills, and attention.

As such, those who use cannabis want to be cautious when it comes to driving. Patients with medical cannabis should be sure to only drive when they feel sober.

But how will law enforcement know if you’re high? That’s where it gets tricky.

With alcohol consumption, breathalyzers and blood tests are reliable measures of intoxication. The presence of alcohol definitively shows that an individual recently consumed alcohol. With cannabis, test results are not quite as straightforward.

Tests that identify cannabis in body fluids identify the quantity of the THC metabolite THC-COOH. But THC-COOH itself is not psychoactive. What this means is that you can have THC-COOH in your system without intoxication. As such, urine, blood, and oral levels of THC are poor predictors of how intoxicated someone is. This is particularly true with low levels of the THC metabolite.

In a recent study in Canada, for instance, researchers examined blood tests from people involved in car crashes. There was no increased risk of crash responsibility in people with THC levels of 1-5 ng/ml.

The difficulty with THC is twofold. First, the quantity of THC that causes mental intoxication varies from one person to the next, and even from one day to the next. On top of that, traces of THC can remain in bodily fluids for weeks after ingestion—long after THC’s effects have worn off. The more marijuana you use and the longer that you use it, the longer residual THC will remain in your system.

In essence, drivers can test positive for THC when they are completely sober. And as many medical cannabis patients use cannabis daily, tests for THC may not be the best way to determine if someone is driving under the influence.

But this hasn’t stopped states from imposing legal limits for THC. Many states have legal limits for driving of 5 ng/ml THC or less. Others have a zero-tolerance policy, with any detectable THC paving the way for a DUI.

Fortunately, Arkansas law presently has no legal limit, known as a per se limit, for THC. What this means is that an officer should use sobriety tests, rather than bodily fluid tests, to identify cannabis intoxication.

This is good news as roadside tests for motor or mental impairment appear to be more useful than tests that measure THC levels in the body. But the inability to properly test for cannabis intoxication does create a grey area for cannabis DUIs.

When it comes to driving after using medical marijuana, be cautious. The best indicator that it is okay to drive is when you feel completely sober.


If you are an Arkansan suffering from one of these 18 medical conditions you may be eligible to treat your ailment with medical marijuana, which includes both THC and CBD products.

Click here to learn more about what Arkansas Marijuana Card's state-certified medical marijuana doctors can do for you, or give us a call at (844-249-8714) and our friendly support team can walk you through the entire process, and set you up with an appointment.

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