Researchers at Massachusetts General Hospital (MGH) have discovered a noninvasive method to detect THC (tetrahydrocannabinol) intoxication and published the findings in the journal Neuropsychopharmacology. Brain activity was assessed by functional near-infrared spectroscopy (fNIRS) in order to identify activation patterns that suggest impairment.
Researchers scanned the brains of 169 study participants before and after giving them oral THC or a placebo. Participants who reported intoxication after ingesting the oral THC demonstrated increased oxygen hemoglobin concentration (HbO) levels compared to participants reporting no or little intoxication. According to principal investigator Dr. A. Eden Evins, “[t]he accuracy of this method was confirmed by the fact impairment determined by machine learning models using only information from fNIRS matched self-report and clinical assessment of impairment 76 percent of the time.” The findings suggest brain imaging can provide reliable evidence confirming impairment.
Researchers hope to refine brain scanning technology so that it can distinguish THC levels indicating mild cannabis exposure from harmful intoxication, since equipment specifically designed for cannabis detection is critical for accurate and fair assessments. Early detection devices were modeled after alcohol breathalyzers, but they are not suitable for determining cannabis intoxication. The alcohol level in the lungs correlates with the alcohol level in the rest of the body and this information is used to calculate a specific threshold level of impairment. THC concentration in the body does not correspond well to functional impairment in the same way that alcohol concentration corresponds to impairment. Therefore, respiratory methods of cannabis detection are not accurate, because they do not determine when a person last consumed and how the amount of consumed cannabis correlates to the threshold of impairment. Metabolites of THC can stay in the bloodstream for weeks after use, so it is difficult to associate poor driving or unsafe workplace behavior with an exact timeframe of cannabis intoxication. Saliva tests are also not reliable; they can detect the presence of cannabis, but not the amount and thus the exact level that indicates impairment. Advances in brain imaging offer more efficient and precise ways for law enforcement to assess functional impairment.
The MGH researchers believe this brain-based method procedure will provide a more objective and practical assessment than currently available detection testing methods. The portable, lightweight, battery-operated brain imaging device can be used by employers and law enforcement to increase efficiency and safety in the workplace and on the roads.
Sources:
Massachusetts General Hospital, Nation World News, Nature