CBD products are more and more popular, but new research suggests that some products with CBD may cause positive drug test results. This new (very small) study from a team at Johns Hopkins Medicine could be cause for worry.

The researchers administered pure CBD to six adults, both orally and via vaporizer. At different times, the subjects also inhaled vapor from CBD-dominant cannabis containing 0.39 percent THC. The subjects then gave urine samples according to common standards for drug testing.

The pure CBD did not produce a positive result. However, in 2 of 6 subjects, the CBD-dominant cannabis vapor did cause the result.

Wait—Is that really hemp/CBD?

Hold on, you might be thinking. There actually was a little too much THC in there according to the law! Isn’t that why that CBD may cause positive drug test results in the first place? This is partly why the scientists are concerned.

Most conventional drug tests for cannabis use urine samples. These tests look for THCCOOH, a common metabolite of THC. Since many CBD-dominant products—especially “full-spectrum” products—contain small amounts of THC, this might be a problem for many consumers.

Even hemp-derived CBD products can contain up to 0.3 percent THC by law, so the cannabis the team used is close—but still over the limit to start with. It’s also cannabis, not hemp, so it’s illegal at the federal level anyway. However, its THC concentration of 0.39 percent is just 0.09 higher than the regulated level.

However, the bottom line is that people who regularly use CBD products, especially full-spectrum products, could possibly fail a test if this research holds up. This is in line with other research we’ve seen on other cannabinoids.

The researchers also point out in the press release that it is possible that repeated use of CBD products may cause accumulation of THC and its metabolites.

“People who use legal hemp products for medical intent rarely just use them once as we did in this study, and prior studies show that THC and its metabolites may accumulate with repeated use,” postdoctoral fellow Tory Spindle, Ph.D., a researcher in the Behavioral Pharmacology Research Unit at the Johns Hopkins Bayview Medical Center, said in the press release. “What this means is that people need to be wary of single-dose or cumulative THC exposure and be aware that these now legal products may cause an unexpected positive result on a drug test.”

Sample size, regulation problems

The other problem with the study, of course, is that there were only six people in it, total. Please see our commentary on why this sample is too small here. However, given how difficult it is in the US to fund any sort of research concerning cannabis and cannabinoids, this is not necessarily surprising.

The team also concludes that despite the size and dynamism of the market for hemp and CBD products, it remains mostly unregulated. In fact, this appears to be the crux of their point.

“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,” says Ryan Vandrey, an associate professor of psychiatry and behavioral sciences at the Johns Hopkins University School of Medicine. “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.”

The Substance Abuse and Mental Health Services Administration (SAMHSA) and the National Institute on Drug Abuse (NIDA) supported this research (T32DA07209).

One of the researchers, Dr. Vandrey, an associate professor of psychiatry and behavioral sciences at the Johns Hopkins University School of Medicine, named potential conflicts. He has “been a paid consultant for or received honoraria” from Canopy Health Innovations Inc., FSD Pharma, and Zynerba Pharmaceuticals.

The first two are actually cannabis-related health companies, and the third is a traditional pharmaceutical company. The potential conflicts were disclosed right in the work.