In a small study, half of patients who had taken CBD oil for four weeks had a positive urine test for THC, the psychoactive ingredient in marijuana, although none of them reported feeling high. Seven of 14 patients taking part in a clinical trial to test the efficacy of cannabidiol (CBD) to treat anxiety ended up with a positive urine test for a major metabolite of delta-9-tetrahydrocannabinol (THC) even though the levels of THC in the product they were given were far lower than the amount found in legal hemp-derived products. "People think because CBD is legally sold they won't test positive in a urine screen," said Staci Gruber, an associate professor of psychiatry at the Harvard Medical School and director of the Cognitive and Clinical Neuroimaging Core and Marijuana Investigations for Neuroscientific Discovery (MIND) at McLean Hospital in Belmont, Massachusetts. "But this tells us that that is not necessarily true." To take a look at whether CBD oil could impact urine tests for marijuana, Gruber and her colleagues tapped a group of patients who were taking part in a clinical trial testing the hemp-derived product as a possible treatment for anxiety. The 14 volunteers, aged 18 or older, all suffered from anxiety and all tested negative for THC at baseline. The study product was formulated using a full-spectrum, high-CBD extract containing 9.97mg/mL of CBD and 0.23 mg/mL of delta-9-THC. The patients self-administered 1 mL of the study product sublingually three times a day for a targeted daily dose of 30 mg of CBD and less than 1 mg of delta-9-THC. As reported in JAMA Psyciatry, the researchers kept track of the amount of CBD oil the participants were using by weighing outgoing and incoming bottles of the product and cross referencing that information with weekly drug diaries kept by the participants. The study drug was well tolerated, and the patients reported no serious adverse events or psychoactivity. Patients used an average of 3.48 mL of the CBD oil per day, which was equivalent to an average of 34.73 mg of CBD per day and 0.80 mg of delta-9-THC per day. When the researchers ran a urine screen on the 14 participants after four weeks, they found that seven tested positive for the metabolite THC-COOH, while seven tested negative. When the researchers tested samples with gas chromatography-mass spectrometry, they found that while the results of the urine tests were valid, the screens were often more sensitive than their stated lower limit of detection (50 ng/mL). The positive screens could not be explained by BMI, age, sex, race, or medication use. They were associated only with creatinine levels. "That half the sample tested positive was surprising," Gruber said. "And it's something people have to be mindful of because testing positive may have legal and employment ramifications." The new paper is "interesting," said Dr. Michael Lynch, medical director of the Pittsburgh Poison Center at UPMC. "And it does what all small studies should do: it raises a question that requires further investigation." There are two possible explanations for the failed screening tests, Dr. Lynch said: either the THC is for some reason building up or some of the participants may have had an alternative source of THC that was not accounted for. The association with creatinine levels may point to an issue with the kidneys which might be producing more concentrated urine, Dr. Lynch said. If further studies show that THC is building up over time in some individuals, then that needs to be accounted for in some way by organizations that do testing, Dr. Lynch said. —Linda Carroll Source
