St. John's wort (Hypericum perforatum) is a plant with yellow flowers that has been used to treat depression in European countries for centuries. It is sold in liquid and powder (pill) form and can be found at health food stores and pharmacies.

A person who wants to try St. John's wort should first talk to his or her doctor because it may interfere with treatment for other conditions. Also, herbal products are not regulated in the United States, so ingredients and quality can be inconsistent.

A person should not take St. John's wort while taking:

• Other antidepressants. Taking both can result in serious, negative side effects.
• Protease inhibitors (PIs) or nucleoside reverse transcriptase inhibitors (NRTIs) for the treatment of HIV infection.