Biomarkers of Recent Cannabis Use in Blood, Oral Fluid and Breath

Proving driving under the influence of cannabis (DUIC) is difficult. Establishing a biomarker of recent use to supplement behavioral observations may be a useful alternative strategy. We determined whether cannabinoid concentrations in blood, oral fluid (OF) or breath could identify use within the past 3 h—likely the period of the greatest impairment. In a randomized trial, 191 frequent (≥4/week) and occasional (<4/week) cannabis users...