St. John’s Wort

St. John’s wort has been used to treat various conditions for over 2,000 years. Currently it is most commonly used in treating depression. The active compounds in St. John’s wort have not been clearly established, although hypericin or hyperforin have both been suggested to produce the herb’s therapeutic effects. St. John’s wort may have multiple biological effects, but the mechanisms underlying these actions are not well understood.

The effectiveness of St. John’s wort as an antidepressant has been studied extensively. A study was published that combined the information from 27 previous studies on St. John’s wort and depression. The quality of some of these studies has been called into question. This study reported that St. John’s wort may act as an antidepressant in people with moderate or mild depression. It is not clear whether it is effective for people with severe depression.

Two recent studies have further investigated St. John’s wort as an antidepressant. One study found that the effects of St. John’s wort were similar to a placebo for people with mild or moderate depression. It is possible, however, that this study was not large enough to discriminate between the effects of these compounds. Another study looked at severe depression, using sertraline (Zoloft), St. John’s wort, and a placebo. Neither setraline nor St. John’s wort appeared to be more effective than the placebo. The effectiveness of St. John’s wort needs to be further investigated.

People considering St. John’s wort should discuss this herb with their physician. As depression can be a very serious condition, a person who is feeling depressed should consult a physician. St. John’s wort should not be used for severe depression. It is generally well tolerated, but may cause dizziness, sedation, upset stomach, confusion, and anxiety. In rare cases, this herb has produced photosensitivity, a hypersensitivity to sun exposure that affects the skin and nerves. This is more likely to occur in people with fair skin. St. John’s wort may cause mania or hypomania in people with depression or manic-depressive illness. Withdrawal side effects, such as dizziness, nausea, headaches, fatigue, insomnia, and confusion, may occur if use of St. John’s wort is abruptly discontinued.

St. John’s wort may also interact with many medications. This herb acts on the liver, and may actually decrease the blood concentration of certain prescription drugs, including oral contraceptives and blood-thinning medication. St. John’s wort may also affect drugs used for seizures, heart disease, depression, and cancer. Furthermore, several drugs used to treat MS-associated symptoms may be affected. St. John’s wort should not be taken while taking antidepressant medications.

St. John’s wort is generally taken in 300mg doses, three times per day. The standardized tablet contains 0.3% hypericin.

References and Additional Reading


Bowling AC. Complementary and Alternative Medicine and Multiple Sclerosis. New York: Demos Medical Publishing, 2007.

Bowling AC, Stewart TS. Dietary Supplements and Multiple Sclerosis: A Health Professional’s Guide. New York: Demos Medical Publishing, 2004.

Jellin JM, Batz F, Hitchens K, et al. Natural Medicines Comprehensive Database. Stockton, CA: Therapeutic Research Faculty, 2009.

Ulbricht CE, Basch EM, eds. Natural Standard Herb and Supplement Reference: Evidence-Based Clinical Reviews. St. Louis: Elsevier-Mosby, 2005.


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