Is there evidence that kava quells anxiety? And could there be a downside? “Kava root has a long history of use in Polynesia for its mild sedative effects,” says Craig Hopp, an expert on medicinal plants at the National Center for Complementary and Integrative Health. “But that’s very different from how people are using it today. Kava bars serving kava drinks have sprung up, and you can get kava as a dietary supplement.”