The percentage of THC in the blood is not a reliable indicator for the ability to drive according to the American National Institute of Justice

thc driving

Field sobriety tests and THC levels are not reliable indicators for determining ability to drive

Researchers have studied how THC affects the skills required for safe driving and found that THC levels in body fluids do not correlate with field sobriety test results. No matter how the cannabis has been ingested. This in-depth study published by the US Department of Justice found that the percentage of THC in the body is not a measure of ability to drive. This is especially interesting especially in countries like France where the police use saliva tests to detect THC, and the study results actually nullify the value of this test. Interesting findings that contradict the very principle of testing THC in devices as a measure of driving ability.

Differences in the detection of the presence of cannabis and its quantification depending on the route of administration

Laws relating to driving under the influence of cannabis vary from state to state, yet states have laws that use the drug. level of delta 9 tetrahydrocannabinol in blood, urine or saliva as determinant. However, there is little evidence to link a THC level to impaired driving, making these laws controversial and difficult to enforce.

In an effort to better understand the presence of psychoactive substances and ultimately improve legislation, researchers from RTI International, funded by the National Institute of Justice, investigated how specific cannabis doses and methods of administration (eaten or vaporized) affect THC levels in the body and how this correlates with performance on impairment tests.

The results of their dosage study clinical research showed that THC levels in participants' biofluids varied depending on both dose and consumption method. It also involved understanding when maximum impairment was reached for which dose and examining test performance. Therefore, the RTI team concluded that while there is evidence that THC affects areas of the brain that control movement, balance, coordination, memory and judgment, i.e. skills required to drive, the levels of THC in the biofluids were not reliable indicators of impaired driving skills for the participants.

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Design and results of the THC dosage study

In six double-blind clinical dosing sessions, RTI researchers evaluated how oral and spray administration of known doses of THC affected behavior and performance, as well as forensic toxicology testing of blood samples. , urine and oral fluid in 20 study participants.

Each of the participants performed the six dosing sessions. they have ate cannabis brownies containing 0,10 and 25 mg of THC and inhaled vapor containing 0,5 and 20 mg of THC. The dosing sessions were spaced at least one week apart.

Cognitive and psychomotor effects of THC

The cognitive and psychomotor performance of the study participants was assessed using common impairment tests - none of which are currently part of a legal protocol to determine the degree of intoxication - before and after administration. THC, including:

  • Paced series addition test.
  • Digital symbol substitution test.
  • Divided attention test.
  • DRUID iOS smartphone application tasks 1 to 4.
  • Standardized field sobriety tests to detect alcohol impairment, including standing on one leg, walking and turning, modified Romberg's balance, and eye monitoring for nystagmus and pupillary response.

After taking THC, study participants reported experiencing increased effects with increasing doses of cannabis. These subjective effects peaked on average three to five hours after oral administration and zero to one hour after administration by spray.

The cognitive and psychomotor functions of the study participants were negatively affected after all doses of cannabis given by mouth or by vaporization, except for the lowest dose, which contained 5 mg of THC.

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For THC doses above 5 mg, the strongest cognitive and psychomotor effects were observed between zero and two hours after administration and returned to baseline after four hours.

For oral THC doses, cognitive and psychomotor effects were observed one hour after administration and peak effects were observed approximately five hours after administration. Participants' cognitive and psychomotor functions returned to baseline eight hours after oral administration.

The researchers indicated that Romberg's stand-on-one-leg, gait and spin, and altered balance tests were not sensitive to cannabis poisoning for any of the study participants. .
Testing biofluids for THC

Blood, urine, and oral fluid samples were taken from study participants before cannabis administration, and then almost hourly for eight hours after administration. The researchers sent all of the biological fluid samples to commercial forensic toxicology labs to be analyzed for THC as well as the non-psychoactive components of cannabis, cannabidiol and cannabinol.

Toxicological test results showed that the levels of the three targeted cannabis components (THC, cannabidiol and cannabinol) in the blood, urine and oral fluids were not correlated with measures of cognitive or psychomotor impairment for administration of oral or vaporized cannabis.

Conclusions and implications for law enforcement

RTI concluded that, for their dosing study, the levels of THC in the biofluid were not reliable indicators for determining whether cannabis renders unfit to drive. Many of the participants in their study had significant decreases in cognitive and psychomotor functions even though their blood, urine, and oral fluid contained low levels of THC. The researchers also observed that standardized field sobriety tests commonly used for detect driving under the influence of drugs or alcohol were not effective in detecting the level of "toxicity" of thc.

RTI researchers hope their work will help shape policy around cannabis impairment and driving under the influence of drugs or alcohol.

Tags : conductDoseSide effectsEtude
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