CBD Users May Test Positive for Marijuana on Urine Drug Screen

Megan Brooks

November 06, 2020

A new study discounts the assumption that people who use hemp-derived products will test negative for delta-9-tetrahydrocannabinol (THC), the psychoactive ingredient in marijuana.

The small study found that THC was present in half of urine samples from individuals who had used cannabidiol (CBD) oil for a month.

"It is often assumed individuals using hemp-derived products will test negative for THC," note Staci Gruber, PhD, of McLean Hospital and Harvard Medical School, Boston, Massachusetts, and colleagues.

"[Our] results indicate this may not be true, especially if assays are more sensitive than advertised, underscoring the potential for adverse consequences, including loss of employment and legal or treatment ramifications, despite the legality of hemp-derived products," they write.

The study was published online November 4 in JAMA Psychiatry.

CBD Use Increasing

The popularity of CBD products, especially those derived from hemp sources, is increasing exponentially. Yet few studies have directly assessed whether the use of products with high levels of CBD could lead to positive results on urinary drug tests for THC.

Gruber and colleagues studied 14 adults (11 women) aged 18 years and older who are participating in an open-label, clinical trial testing the use of a high-CBD product for anxiety.

At baseline, all 14 persons tested negative for THC–carboxylic acid (THC-COOH), a major metabolite of THC. The CBD product was formulated using a full-spectrum, high-CBD extract containing 9.97 mg/mL of CBD and 0.23 mg/mL of delta-9-THC.

The patients self-administered 1 mL of the product sublingually three times daily to achieve a targeted daily dose of 30 mg of CBD and less than 1 mg of delta-9-THC. The dosage was quantified using outgoing, rather than incoming, bottle weights and was cross-referenced with weekly drug diaries.

The CBD product was well tolerated with no serious adverse events or psychoactivity. Participants used an average of 3.48 mL of the CBD oil daily, equivalent to an average of 34.73 mg of CBD and 0.80 mg of delta-9-THC each day.

After 4 weeks, seven participants (50%) tested positive for THC-COOH on a urinary drug screen. Gas chromatography–mass spectrometry results confirmed the assay findings but also showed that the drug screen was often more sensitive than its stated lower limit of detection (50 ng/mL).

The authors say it's important to note that the CBD product used in the study contained 0.02% of delta-9-THC by weight; in the United States, hemp-derived products can legally contain up to 0.30% of delta-9-THC by weight, more than 10 times the amount in the study product.

"Pivotal" Research

Reached for comment, Tory Spindle, PhD, researcher with Johns Hopkins University School of Medicine, Baltimore, Maryland, said he was a "little bit surprised that half of participants tested positive, but we really had no data to know one way or the other, so this is a really pivotal study."

Spindle, who wasn't involved in the study, agrees that the findings could have important implications.

"Even though cannabis is becoming legalized in more places, there are many occupations that still do drug testing," said Spindle. These include safety-sensitive occupations, criminal justice occupations, and jobs in the federal government.

"These results are suggesting that it's really difficult to say whether someone tested positive because of exposure to a legal source, which would be hemp, or an illegal source, which might be cannabis," he noted.

Spindle said larger studies are needed to confirm the findings, to determine who might be most likely to test positive after using CBD products, and to see whether certain biomarkers could distinguish use of hemp from use of cannabis.

"Maybe there us a ratio of THC to CBD that would suggest someone was using a hemp product vs a THC product," he noted.

Funding support for the study was provided by private donations to the Marijuana Investigations for Neuroscientific Discovery (MIND) program at McLean Hospital. The cannabis extract base for the study drug was provided by the National Institute on Drug Abuse. The authors and Spindle have no disclosed relevant financial relationships.

JAMA Psychiatry. Published online November 4, 2020. Full text

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