Cannabis plants contain a class of compounds called cannabinoids. “We’ve identified just over 100 of them,” says Daniele Piomelli, professor of anatomy and neurobiology at the University of California, Irvine.

The two most abundant: tetrahydrocannabinol (THC) and cannabidiol (CBD).


“THC drives the hallmark features of feeling high, like getting the munchies and feeling relaxed, as well as the negative side effects, like feeling paranoid or anxious,” explains Ryan Vandrey, associate professor of psychiatry and behavioral sciences at the Johns Hopkins School of Medicine.

“CBD can produce drug effects, but it’s not the typical marijuana high,” notes Vandrey. “It’s not intoxicating, and it doesn’t come with THC-like side effects.”

The evidence for CBD is scant

You can buy CBD as an oil, but it’s also sold in everything from water and candy to Willie Nelson’s CBD-infused coffee.

“CBD is promoted as this amazing, natural, healing product,” says Vandrey. “But many claims about CBD haven’t been substantiated in humans.”

Not that CBD is worthless. Last year, the FDA approved a high-dose CBD drug to treat seizures in two rare severe forms of epilepsy. But beyond that, the evidence is preliminary.

Only a few studies have looked at whether CBD relieves anxiety

In one trial, 57 Brazilian men were randomly assigned to take a placebo or 150, 300, or 600 milligrams of CBD 90 minutes before giving a speech. Oddly, only those who took 300 mg reported lower anxiety during—but not before or after—the speech than placebo takers. (Most of the study’s authors had ties to the CBD industry.)

No long-term trials have tested CBD for occasional anxiety or to treat people with a diagnosed anxiety disorder.

And most studies have used doses of 100 mg or more. Few CBD products have more than 20 mg per dose.

“People are throwing CBD at every condition under the sun at random doses and expecting it to work,” says Vandrey.

“There are a lot of possibilities for CBD,” notes Piomelli, “but they require controlled clinical trials. The smoking gun isn’t there yet.”

CBD can interfere with medicines

In animal and test-tube studies, CBD blocks some forms of an enzyme—cyto­chrome P450—that metabolizes many medicines, including some statins, calcium channel blockers, and antidepressants.

“We know that CBD can affect the metabolism of drugs, though the extent to which that happens is still not well understood,” says Vandrey.

If you’re considering taking CBD, ask your doctor or pharmacist if it can interfere with your medications. (They should be able to tell you if your medication is metabolized by the same enzyme that CBD blocks.)

Looking for CBD?

Hemp oil is made from hemp seeds and doesn’t have much CBD unless it’s added, because CBD is found in hemp’s leaves and flowers (not its seeds). If you want CBD, look for CBD or cannabidiol listed on the label. If a label lists "cannabinoids," there's no way to know how much of that is CBD or if the product simply contains other types of cannabinoids.

But even if you find a product that lists CBD, there's no guarantee that the amount it lists is correct. For example, only about 30 percent of 84 CBD products that Vandrey bought online were accurately labeled.

“Some contained little to no CBD,” he says. And roughly one in five had detectable levels of THC. “It’s quite possible that the therapeutic benefits people are reporting from CBD are driven by THC, or maybe something else entirely.”

Photo: Matthew Brodeur/