Case Report: Sustained Smoking of CBD-Rich Cannabis Yields a Positive Drug Test for Carboxy-THC

Turin, Italy: The sustained smoking of CBD-rich cannabis containing only trace percentages of THC will trigger a positive urine test result for carboxy-THC, according to a case report published in the journal Forensic Science International.

Italian investigators assessed toxicological screens in a single subject who inhaled one CBD-rich cigarette per day (six percent CBD and 0.2 percent THC) over a 26-day period.

Investigators reported that the subject tested positive for the presence of carboxy-THC in urine at levels above 15ng/ml by the fifteenth day of the trial. By contrast, repeated dosing was not associated with a positive oral fluid test for THC. Hair samples also tested negative for both the presence of THC and carboxy-THC.

Authors concluded: “[T]his study based on a single subject suggests that the repeated exposure to CBD-rich cannabis (containing small amounts of THC) can generate positive results when biological samples are tested. In particular, positive urine results for THC-COOH, using the confirmatory cut-off of 15 ng/mL, were obtained after a 15-days period of consumption. These results show the potential risk for chronic CBD-rich cannabis users of failing a urine drug test.”

The report’s findings are consistent with those of a recently published paper in JAMA Psychiatry reporting that the consumption of hemp-derived CBD products that comport with federal standards (containing no more than 0.3 percent THC) can similarly trigger a positive urine test result for marijuana exposure.

Full text of the study, “Determination of cannabinoids in urine, oral fluid, and hair samples after repeated intake of CBD-rich cannabis by smoking,” appears in Forensic science International.