Segmental Hair Analysis for 11-Nor-9-Tetrahydrocannabinol-9-Carboxylic Acid and the Patterns of Cannabis Use

This study aimed to detect 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THCCOOH) in segmental hair to evaluate cannabis use patterns. Hair samples were processed and analyzed using gas chromatography–tandem mass spectrometry. Results showed that THCCOOH concentrations decreased from the proximal to distal hair segments. There was a poor correlation between THCCOOH levels in hair and self-reported cannabis use due to the low accuracy of self-reported data. Despite this, the study provided preliminary insights into the dose and frequency of cannabis use among users in the country.