- Studies of mild to moderate depression have usually used an extract containing 0.3% hypericin. The dose has usually been 300 milligrams (mg) three times a day, although doses of 1,200 mg a day have also been tried. Other studies have used doses of 250 mg twice a day of 0.2% hypericin extract. There has also been research using 300 mg three times a day of an extract with 5% hyperforin content. The dose used in trials with children under age 12 has been 300 mg a day of 0.3% hypericin extract.
- One study of obsessive-compulsive disorder used an extended-release 0.3% hypericin extract with a dose of 450 mg twice a day.
- One study of premenstrual syndrome used 300 mg once a day of 0.3% hypericin extract.
- Research on physical symptoms associated with depression has used 300 mg three times a day.
- In studying somatization disorder (a chronic condition in which no physical cause can be found for physical symptoms involving more than one part of the body), 600 mg a day of one particular extract (LI 160, Lichtwer Pharma) has been used.
There is no recommended dosage for external application (applying to the skin) of St. John's wort.