Scientists Have Created A New Way To Test For Cannabis Use

Blood testing for tetrahydrocannabinol (THC) has been the standard for years. It’s not uncommon for police to use these to try and determine if someone was under the influence after a car accident, but these tests can’t accurately determine when someone last smoked. Regular cannabis consumers can have detectable THC levels in their blood for days or weeks after use, making this a shaky form of evidence that may unfairly convict someone who wasn’t high while driving.

With cannabis legalization and reform sweeping the nation, governments have been trying to find more accurate ways to test for recent THC use. After several years of funding and research, scientists at the University of Colorado may have finally found a solution.

“There has been a lot of concern about whether the use of cannabis has been associated with an increased risk of motor vehicle crashes or accidents in the workplace,” said Professor Michael Kosnett.

Since THC is a fat-soluble substance, it can build up and get stored in body fat for some time after use. Urine and blood cannabis tests look for a metabolite called carboxy THC (THC-COOH), which is not psychoactive. To determine more recent use, researchers instead looked at the molar metabolite ratio of THC to THC-COOH. In layman’s terms, they compare the rate of psychoactive to non-psychoactive metabolites in blood.

To test their new method, the scientists gathered 32 daily cannabis users, 24 occasional users, and a control group that doesn’t use marijuana at all. They then measured blood THC levels before consuming cannabis, 15 minutes after, and 30 minutes after while also having participants perform a simulated driving test. They found that the cannabis tests were about 96% accurate at detecting recent use.

There is still some work to be done developing these tests so they can be performed within a few hours of consumption since most people won’t have blood tests administered 30 minutes after smoking. However, these results are encouraging, and researchers are excited to continue progressing.

If tests like these become mainstream, they could help prevent regular cannabis users from being convicted by being able to definitively prove that they weren’t high during a car or work-related accident.

“We think it is pretty important news,” said Kosnett.