St. John’s Wort
(See also Overview of Medicinal Herbs and Nutraceuticals.)
The reddish substance in the plant’s flowers contains numerous biologically active compounds, including hypericin and hyperforin.
People take St. John’s wort mostly to relieve symptoms of depression. Study results vary, but there may be a benefit in treating mild to moderate short-term depression.
St. John’s wort has been used in the treatment of skin disorders, including psoriasis, but its effectiveness in treating this disorder is unproved.
St. John’s wort may cause increased sensitivity to sunlight. Other side effects include digestive tract symptoms, fatigue, and mania (in people with bipolar disorder). Pregnant women should not take this supplement because it increases muscle tone in the uterus and thus may increase the risk of a miscarriage.
One of the larger problems with St. John’s wort is that it may interact negatively with a number of drugs people take (see Table: Some Possible Medicinal Herb–Drug Interactions). These interactions may lead to toxic reactions or ineffectiveness of the drug.