Lindsay Bourque writes:
Hypericum, the genus to which this species belongs, has been used for centuries as a herbal remedy documented in Aulus Cornelius Celsus’ (circa 25 BC- 50 CE) De Medicina. Known in English by its common name, St. John’s Wort, it is used for its anti-bacterial and anti-fungal properties.
Contemporary pharmacology has isolated two compounds, hyperforin and hypericin, which are used to treat mild depression. Interestingly, in ancient Greece Hypericum was hung above pictures to ward off evil spirits (hyper-above and eikon-a picture). However, its effectiveness as an anti-depressant is still debatable and has a number of known side-effects, such as photosensitivity.