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Full-Spectrum CBD Products Can Still Return Positive Cannabis Results, Research Finds

By Alexander Beadle

Published: Nov 11, 2020   
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The amount of THC present in legal full-spectrum CBD products is so low that there is no way a consumer could ever test positive on a drug test, right? That’s the assumption many CBD consumers have been acting under ever since the Farm Bill legalized the production and sale of these hemp-derived products in the US.

But a new research letter published in JAMA Psychiatry is calling that assumption into question. After conducting an open-label clinical trial, the researchers found that half of all participants who consumed a full-spectrum high-CBD product ended up testing positive for cannabis use on a urinary drug test after a short period of consistent use.

Fifty percent test positive despite very low THC content in the product

The researchers were working with a sublingual (under-the-tongue) full-spectrum CBD tincture, which is currently in phase two clinical trials, that is meant to be used as an adjunct treatment for anxiety in adults. The recommended dosage for the tincture is three times per day for a duration of four weeks, in addition to other anti-anxiety treatments a patient may be on.

The study included 14 adult-age patients who completed the four-week treatment course, all of which reported zero cannabis use and at least moderate levels of anxiety at the beginning of the study period. The CBD tincture they were given contained around one percent CBD and just 0.02 percent THC; the mean dosage per day was calculated to be around 6.03 milligrams and 0.14 milligrams of CBD and THC, respectively. No participants reported any serious adverse events or psycho-activity.

The study participants submitted urine samples for a THC test, which works by detecting the presence of the THC metabolite 11-nor-9-carboxy- Δ9-tetrahydrocannabinol (THC-COOH). The assay results were also confirmed using gas chromatography-mass spectrometry analysis at a third-party lab.

After four weeks of following the recommended dose guidelines, seven of the fourteen participants tested positive for THC-COOH. Logistic regression analysis did not find any correlation between THC-positive status and other demographic variables, such as age or BMI, although there was a significant association with creatinine levels, which is reflective of kidney function and hydration. The researchers caution that this association still needs to be assessed further in a larger sample size with a more diverse demographic.

Drug screening may also be more sensitive than advertised

The gas chromatography results confirmed the THC-positive status of the participants, but it also indicated that the drug screening assay was often more sensitive that its stated lower limit of detection, around 50 nanograms per milliliter.

This sensitivity matters because the product used in the study only contained 0.02 percent THC by weight; in the US, hemp-derived products can legally contain up to 0.3 percent THC by weight, more than 10 times the amount included in the study product. This raises the possibility that individuals using perfectly legal full-spectrum CBD products might still find themselves testing positive for cannabis if asked to take a routine drug test – something that could be particularly troublesome in areas where cannabis use is not yet legalized or decriminalized.

“It is often assumed individuals using hemp-derived products will test negative for THC,” the scientists wrote in their research letter. “Current 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.”

CBD products have been linked to positive tests before

While this is the first study to look at how drug test results might be affected by the consistent use of full-spectrum CBD products, it is not the first to suggest that CBD products might cause issues with returning positive tests.

In a previous short-term study, researchers looked at the one-off use of vaping high-CBD, low-THC cannabis and the subsequent drug test results. The cannabis material used in this study contained a much higher level of THC than that used in the new JAMA study, coming in at around 0.39 percent by weight. While this does not quite meet the legal definition for hemp, the material did contain a CBD-to-THC ratio of 27:1, similar to the composition of many CBD or hemp products.

In this study, the participants vaporized less than a gram of cannabis material, resulting in a dose of around 100 milligrams of CBD and 3.7 milligrams of THC. Two of the six study participants then tested positive for a cannabis metabolite during drug screening.

“I have a hard time finding anyone who hasn't used a CBD product at least once, but most are completely unaware of the possibility of THC exposure or a positive drug test as a result of using these newly legalized products,” said the study’s lead author Ryan Vandrey said in a statement at the time.

“Because the market for CBD products is so new and the popularity of use is growing so quickly, we want the public to be aware that a positive drug test is possible.”


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