Touted as a treatment for a wide range of conditions — including anxiety, pain, inflammation and even cancer — CBD may be the latest version of snake oil. Or perhaps a real relief for numerous ailments.

Nobody really knows which is true because there has been so little solid research on CBD's effect on humans, experts say.

CBD, or cannabidiol, comes from the hemp plant, a close relative to another member of the cannabis family, marijuana. Both plants contain abundant types of cannabinoids, but marijuana is high in the psychoactive chemical THC, while hemp is rich in CBD, which doesn’t create a buzz but may offer a range of medicinal benefits.

Even without research to back it up, the trendy CBD has been turning up in a vast array of products, including CBD-infused lattes, massage lotions and baked goods. And that means it’s becoming big business, with sales expected to hit $20 billion in the next few years.

Thus far, there is only one use for CBD approved by the Food and Drug Administration, and that’s as a treatment for two rare forms of epilepsy. But that doesn’t stop true believers like Dr. Joseph Cohen, who runs a cannabis clinic in Boulder, Colorado, from making enthusiastic claims.

“It works for anxiety, it works for pain, it works for inflammation, it works for autoimmune disorders, and there's a slew of other conditions for which you can get benefit,” said Cohen, a former gynecologist.

There’s no clear evidence that CBD works for any of those things, experts told NBC News. “We don’t know any of that,” said Dr. Margaret Haney, a professor of neurobiology at Columbia University Medical Center and director of Columbia’s Marijuana Research Laboratory.

“There’s an enormous placebo effect,” she said. "If you go in with this expectation, with all of society saying this will cure whatever ails you, it often will."

Dr. Jeffrey Chen seconds that opinion. “Certainly there is therapeutic potential from CBD, but the amount of human data is minuscule, and popular access and consumption have far outpaced the science,” said Chen, executive director of the Cannabis Research Initiative at the University of California, Los Angeles. “So if you’re going to take it, you have to understand there is little data and you have to be very careful about the source and you need to talk to your doctor about how it might interact with other drugs you are taking.”

With no one regulating cannabinoids, you often can’t be sure what dose you’re actually getting, Chen said. He recommends buying from medical marijuana dispensaries, which are regulated by local governments.

While FDA testing of CBD for use in epilepsy showed that the chemical was relatively safe and free of side effects, it does appear to interact with other drugs, including antidepressants known as SSRIs and blood thinners, boosting their levels in a person’s system because it inhibits an enzyme that breaks them down, Chen said.

Studies in animals suggest that CBD might help with anxiety, pain and inflammation, but Chen is quick to point out that “the majority of times when we see promising drugs in animals they either don’t work in humans or they have horrible, horrible side effects.”

One thing experts do know is that unlike THC, CBD doesn’t hook onto cannabinoid receptors in the brain or body, said Michael Zemaitis, a professor of pharmaceutical sciences at the University of Pittsburgh.

Instead, it appears to affect enzymes that break down endogenous cannabinoids — the ones made by our own bodies.

“It seems to have a very broad dampening effect,” Zemaitis said. “That’s part of the reason why you see so many indications” for their use.

In that sense, the effects of CBD are very different from those of opioids, which have specific receptors to plug into, turning on cell machinery in much the same way a key in a car ignition turns on the engine.

There is little information about the medicinal effects of both THC and CBD, mainly because of federal laws on marijuana, experts said. Marijuana and its extracts have long been considered Schedule 1 drugs, defined as having no accepted medical use and a high potential for abuse.

That puts any kind of cannabis in the same category as heroin and LSD, which means researchers have to jump through a lot of hoops to even get any cannabinoids to study, Chen said.

Another big concern for experts is that patients will avoid proven medications in favor of CBD.

“We have a long history of people using snake oil to convince people they're getting something,” Haney said. “Then there have been more dangerous situations where people turn down effective medications" to use unproven products, like CBD.

Things may change soon when it comes to CBD, Chen said. The 2018 Farm Bill contains language that will legalize industrial hemp, he said, “so we’ll be able to start generating data on what it will work for and what it will not.”

CORRECTION (Dec. 12, 2018, 12:12 p.m. ET): An earlier version of this article misstated the change in the status of hemp, now classified as a Schedule 1 drug, anticipated in the new Farm Bill. It would be legalized, not reclassified as a Schedule 3 drug.