There are about 500 known species of passionflower. This family of plants is also known as Passiflora. Native Americans have used passionflower to treat a variety of conditions including boils, wounds, earaches, and liver problems. In Europe, and in the US people have used passionflower to treat restlessness and agitation and even anxiety. Scientists believe passionflower works by increasing levels of a chemical called gamma-aminobutyric acid (GABA) in the brain. GABA lowers the activity of some brain cells, making you feel more relaxed.