Cannabidiol -- commonly known as CBD -- might not be all it is touted to be, new research suggests.
Instead, existing evidence on the potential benefits of the compound found in marijuana and hemp has often been backed by industry, scientists said.
The researchers found that of 99 human CBD studies done since 2014, about 62% had some conflict of interest -- including industry funding, or a study author employed by a company that markets CBD products.
And those studies were more likely to reach positive conclusions, versus research with no industry ties.
The findings are not surprising, experts said. It's known from drug studies that industry funding is linked to a greater likelihood of positive results.
But at a time when CBD is showing up in everything from oils and lotions to coffee and cookies -- and consumers tend to see it as "natural" -- the findings may serve as a reminder to remain savvy.
"This gives consumers an idea of where the research is coming from," said study author Joshua Wallach, an assistant professor of epidemiology at Yale School of Public Health, in New Haven, Conn.
So when you hear or read that a study supports CBD for a particular use, he said, you might want to "think critically" about the source of that research.
Wallach also suggested keeping the "bigger picture" in mind. At this point, CBD is approved by the U.S. Food and Drug Administration for only one indication: certain rare forms of epilepsy. In 2018, Epidiolex -- a purified, pharmaceutical-grade CBD -- got the nod for treating the seizure disorders Dravet syndrome and Lennox-Gastaut syndrome.
As for the array of other CBD health claims -- easing conditions like chronic pain, anxiety and insomnia -- the jury is still out. The CBD products being sold in capsules, food and cosmetics have not been evaluated by the FDA.
CBD is one of hundreds of chemicals found in marijuana. It differs from THC, the source of the famous marijuana "high." CBD is present in marijuana but is more abundant in hemp -- cannabis plants that have little THC.
The recent explosion in consumer CBD products is not the result of research evidence, but of a change in federal law. In 2018, Congress lifted a decades-old ban on growing hemp. Licensed farmers can now grow the plant, provided it contains less than 0.3% THC.
For the new study, published online March 17 in the Annals of Internal Medicine, Wallach's team found 417 CBD-related articles published in medical journals between 2014 and 2019.
Most -- 318 -- were either based on lab studies or were commentaries or reviews on existing research. The remaining 99 articles described human studies.
Of those, most focused on neurological conditions (52.5%) or mental health (17%). (Wallach and his colleagues did not break them down by specific indication.) And the majority -- nearly two-thirds -- had some kind of industry involvement, Wallach said.
Industry links, in turn, were related to the likelihood of "supportive" conclusions -- where authors either reported that CBD treatment was effective, or made recommendations on using the compound.
Overall, 74% of those publications came to supportive conclusions, versus about 65% of those without industry involvement, and 55% of articles that made no disclosures about conflicts of interest.
According to Wallach, it all suggests there "could be some spin going on," with some CBD research essentially being used as a marketing tool.
It is also possible that industry-backed research is better done and more likely to yield positive results, according to Dr. Peter Lurie, president of the nonprofit Center for Science in the Public Interest.
It's also unclear how much of the research was specifically related to Epidiolex, he noted.
That said, Lurie agreed that consumers should be aware of who is funding CBD research. "You want research to be conducted," he said. "But whether you want it to be supported by industry is another thing."
Like Wallach, Lurie pointed to the broader issue. "There are health claims about CBD that are completely unfounded," he said. "Outside of its use for epilepsy, I would see everything else as speculative."
The U.S. Food and Drug Administration has more on CBD.