Study identifies potential test for cannabis impairment
Researchers at Massachusetts General Hospital have found a noninvasive brain imaging procedure to be an objective and reliable way to identify individuals whose performance has been impaired by THC, the psychoactive ingredient in cannabis.
The technique uses imaging technology known as functional near-infrared spectroscopy (fNIRS) to measure brain activation patterns that correlate to impairment from THC intoxication. As reported in the journal Neuropsychopharmacology, the procedure could have significant implications for improving highway and workplace safety.
The increased use of cannabis through legalization has created the urgent need for a portable brain imaging procedure that can distinguish between impairment and mild intoxication from THC. “Our research represents a novel direction for impairment testing in the field,” says lead author Jodi Gilman, investigator in the Center for Addiction Medicine, MGH, and associate professor of psychiatry at Harvard Medical School. “Our goal was to determine if cannabis impairment could be detected from activity of the brain on an individual level. This is a critical issue because a ‘breathalyzer’ type of approach will not work for detecting cannabis impairment, which makes it very difficult to objectively assess impairment from THC during a traffic stop.”
THC has been shown in past studies to impair cognitive and psychomotor performance essential to safe driving, a factor thought to at least double the risk of fatal motor vehicle accidents. The challenge for scientists, however, is that the concentration of THC in the body does not correspond well to functional impairment. One reason is that people who use cannabis often can have high levels of THC in the body and not be impaired. Another is that metabolites of THC can remain in the bloodstream for weeks after the last cannabis use, well beyond the period of intoxication. Hence the need for a different method to determine impairment from cannabis intoxication.
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