MADISON, Wis. (AP) — Hemp-derived cannabidiol is gaining steam in Wisconsin for its proclaimed wellness benefits, despite varied quality control and limited scientific research on its use and long-term effects.

Wisconsin in late 2017 joined 33 other states in legalizing hemp farming, Wisconsin Public Radio reported . The 2018 farm bill also designated hemp as an agricultural crop. But the legality of products containing CBD oil, a non-psychoactive compound found in hemp, has been murky, and the U.S. Food and Drug Administration has sent warning letters to some companies making health claims for CBD.

James Valona, one of the owners of Verdant, a Milwaukee store that sells CBD products, said it can be used in everything from candy to oils to ointments. Valona and other CBD aficionados maintain that the product has therapeutic benefits.

"More and more people are talking about it, the effects of CBD are positive on so many people," said Valona. "Some people are taking it because it's assisting with sleep, (for) some it assists with pain. Myself, I take it because I have arthritis in my right knee."

Cecilia Hillard, director of the Neuroscience Research Center at the Medical College of Wisconsin, studies the effects of CBD on the body and brain. While she's optimistic about what research could reveal about CBD's medical potential, Hillard said there are some things consumers should know.

"There's no regulatory agency that's overlooking (CBD oil's) purity, its concentration, whether or not there are other things that are present in the oils like pesticides, or molds, or heavy metals and so forth," Hillard said.

The National Institutes of Health database shows at least 100 studies across the world involving CBD that are either recruiting subjects or active. Other studies in the database are of an unknown status or have been suspended.