Research describes brain-based method to identify cannabis impairment – Harvard Gazette
Researchers at Massachusetts General Hospital have found that a non-invasive brain imaging procedure is an objective and reliable way to identify people whose performance has been impaired by THC, the psychoactive ingredient in cannabis.
The technique uses imaging technology known as near infrared functional spectroscopy (fNIRS) to measure patterns of brain activation that correlate with impaired THC intoxication. As reported in the journal Neuropsychopharmacology, the procedure could have important implications for improving road and occupational 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 THC poisoning.
“Our research represents a new direction for field impairment testing,” says lead author Jodi Gilman, researcher at 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 brain activity at the individual level. This is a critical issue because a “breathalyzer” type approach will not work to detect cannabis impairment, making it very difficult to objectively assess THC impairment during a traffic stop. . “
THC has been shown in previous studies to impair cognitive and psychomotor performance essential for safe driving, a factor believed to at least double the risk of fatal traffic accidents. The challenge for scientists, however, is that the concentration of THC in the body does not correspond well with functional impairment. One of the reasons is that people who use cannabis can often have high levels of THC in the body and not be altered. Another is that THC metabolites can remain in the blood 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.
In the MGH study, 169 cannabis users underwent fNIRS brain imaging before and after receiving oral THC or placebo. Participants who reported poisoning after receiving oral THC showed an increased concentration of oxygenated hemoglobin (HbO) – a type of neural activity signature in the prefrontal cortex region of the brain – compared to those who reported little or no poisoning.
“The identification of an acute impairment due to THC poisoning through portable brain imaging could be an essential tool in the hands of police officers in the field”, explains lead author and lead researcher A. Eden Evins, founding director of the Center for Addiction Medicine. “The accuracy of this method was confirmed by the fact that impairment was determined by machine learning models using only information from the fNIRS self-report and clinical assessment of impairment in 76 % time. “
Although the study did not specifically assess the fNIRS in roadside impaired driving assessments, it cited considerable benefits for such an application. These include the feasibility of inexpensive, lightweight, battery-powered fNIRS devices that can store data on portable recording units or transmit it wirelessly to a laptop computer. In addition, the fNIRS technology could be incorporated into a headband or cap, and therefore requires minimal installation time.
“Companies are developing breathalysers that only measure cannabis exposure, but not cannabis impairment,” says Gilman. “We need a method that will not penalize medical marijuana users or others with insufficient amounts of cannabis in their system to adversely affect their performance. While it requires further study, we believe brain-based testing could provide an objective, practical, and much-needed solution. “
Evins is the Cox family professor of psychiatry at Harvard Medical School.
The study was funded by the National Institute on Drug Abuse.