FRIDAY, Jan. 21, 2022 (HealthDay News) — Functional brain imaging may identify Δ9-tetrahydrocannabinol (THC)-associated impairment in cannabis users, according to a study published online Jan. 8 in Neuropsychopharmacology.

Jodi M. Gilman, Ph.D., from Massachusetts General Hospital in Boston, and colleagues conducted a double-blind, randomized study involving 169 cannabis users aged 18 to 55 years who underwent functional near-infrared spectroscopy (fNIRS) before and after receiving oral THC and placebo at study visits one week apart.

The researchers found that the primary outcome of prefrontal cortical oxygenated hemoglobin concentration was increased after THC in participants operationalized as impaired, regardless of THC dose. Impairment was identified with 76.4 percent accuracy, 69.8 percent positive predictive value, and a 10 percent false-positive rate with machine learning models using fNIRS time course features and connectivity matrices and using convergent classification as ground truth. This exceeded Drug Recognition Evaluator-conducted expanded field sobriety examination (accuracy, 67.8 percent; positive predictive value, 35.4 percent; false-positive rate, 35.4 percent).

“Identification of acute impairment from THC intoxication through portable brain imaging could be a vital tool in the hands of police officers in the field,” a coauthor said in a statement. “The 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.”

Two authors disclosed having a patent pending to use fNIRS to measure intoxication.

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