First isolated in 1940, CBD is one of more than 100 biologically active components called cannabinoids that are in the cannabis plant, and it is the second most abundant cannabinoid after THC. Scientists have long known CBD has anticonvulsant and anti-inflammatory effects, but it was not until recent years that CBD got more serious attention from researchers, who initially were more interested in studying cannabis’s psychogenic components, like THC.

“You don’t get a high from CBD no matter how much you take,” said Sumner Burstein, a professor emeritus of biochemistry and molecular pharmacology at the University of Massachusetts Medical School. It is also not addictive, but there is a possibility CBD will interact poorly or interfere with other medications, he said.

Studies are now getting underway to evaluate whether CBD can alleviate anxiety or post-traumatic stress disorder, or help with substance abuse and tobacco cessation. Leaf Vertical, a biopharmaceutical research company, will explore whether it can enhance cancer therapies. Animal studies suggest its anti-inflammatory effects may have benefits for helping to manage chronic pain or treat arthritis or inflammatory bowel diseases like Crohn’s disease. It is also being looked at for the treatment of autism .

GW Pharmaceuticals, which makes Epidiolex, has a multiple sclerosis drug approved in the United Kingdom that combines CBD and THC, and the company is exploring the combination for other therapeutic applications. It is also studying other uses for CBD alone, including for Rett syndrome, a rare genetic disorder that has devastating neurologic consequences in young children.

But the combination of CBD and THC may be more effective for some conditions than CBD alone, experts caution. While cannabis has shown promise for treating pain syndromes, for example, it is not clear that CBD alone will be an effective pain reliever.

Several researchers said their interest in CBD was piqued by patient inquiries. So many people asked Dr. Michael Van Ameringen, director of an anxiety research center in Hamilton, Ontario, about CBD’s therapeutic potential for anxiety that he decided to review the medical literature, and concluded that “there actually really is very, very little scientific evidence to support its use as a treatment for anxiety at this point.”

Some research has reported promising results in other psychiatric applications. Last year, for example, European scientists reported that patients with schizophrenia who were given 1,000 milligrams of CBD in addition to their regular antipsychotic medications experienced fewer hallucinations and racing thoughts compared with those on a placebo. But other studies of schizophrenia have not found the same benefits.