Some species of St. John's Wort are considered endangered because of their limited distribution and declining populations.  The conservation of this plant varies by location and species. In some parts of the United States,  St. John's Wort is considered to be a noxious weed that grows invasively and crowds out other native plants.

Cherokee Indians used St. John's Wort to induce menstrual cramps and act as an anti-diarrheal. Montagnais Indians used this medicinal plant as a cough medicine.  "The Apache Indians used the pollen in female puberty ceremonies. They used the spike as a torch after dipping it in coal oil.   The fluff was used as tinder, insulation, and baby beds" (Huxtable).  "For centuries, the Europeans have been using it in order to treat a vast number of diseases, like anxiety, colds, depression, flu, hemorrhoids, womb muscle contractions during menstruation, skin infections, and wounds" (Istikoglou, Mavreas, Geroulanos 2010).  "Until the Middle Ages, Hypericum formed a part of many summer solstice rituals.  In the eve of Saint John's day, for instance, people used to hang garlands made of the leaves and flowers of this plant over the doors of houses and churches, to protect them from witches and evil spirits.  People also used to put branches of this plant under their pillows in the eve of Saint John's day, believing that the Saint himself would appear to them in a dream, give them his blessing, and keep death away for the year to come.  The dried leaves of this plant were considered to be protective talismans, used like bookmarks withing the Bible and prayer books" (Istikoglou, Mavreas, Geroulanos 2010).

St. John's Wort is considered to be effective at treating mild to moderate depression and has also been considered to be just as effective as standard anti-depressants.  However more research needs to be done to see how effective it would be at treating severe depression. It has low rates of side effects, and unlike standard depressants, St. John's Wort does not decrease sex drive.  Some mild side effects of this medicinal plant include dizziness, trouble sleeping, diarrhea, restlessness, and skin tingling.  St. John's Wort can increase sensitivity to sunlight and interact with other medications and cause them to be less effective while increasing the side effects from those medications. "In 2000, a pharmacokinetic interaction between SJW and cyclosporine caused acute rejection in two heart transplant patients.  Since then, subsequent research has shown that SJW altered the pharmacokinetics of drugs such as digoxin, tacrolimus, indinavir, warfarin, alprazolam, simvastatin, or oral contraceptives" (Nicolussi, Drewe, Butterweck 2020).