St. John's Wort

Photograph © 2000, Lucy Canter Kihlstrom, PhD.

UC Botanical Garden St. Johns Wort.gif (146415 bytes)Medicinal Parts:  The fresh buds and flowers; the aerial parts collected during the flowering season and dried; the entire fresh flowering plant.

Demonstrated Uses Internally, this herb is used for depression, anxiety; topically for burns and as an antiviral, antibacterial agent.  

A 1999 randomized, double-blind, clinical study of St. John's Wort included 263 moderately depressed patients.  Depression was measured using both the Hamilton Depression Rating Scale and clinical impressions.  The effectiveness of St. John's Wort (1050 mg/day) was compared to imipramine (100 mg/day) and to a placebo after eight weeks of treatment.  Philipp and colleagues found that at an average dose of 350 mg (3 times per day), St. John's Wort was more effective than placebo and at least as effective as 100 mg of imipramine daily in the treatment of moderate depression.

However, a study published in 2001 suggests that St. John's Wort was not effective in the treatment of major depression.  Shelton and his colleagues conducted a randomized, double-blind, clinical trial in 11 medical centers in the U.S.  The 200 adult patients who suffered from major depression received either St. John's Wort (900 mg/day to 1200 mg/day depending on the response after 4 weeks) or placebo for a total of eight weeks.  After eight weeks, there was no difference between the group of patients who took St. John's Wort and the group that took the placebo.  It should be noted that this study has been criticized on several dimensions (Parker-Pope, 2001).  As one example, the study only included the herbal remedy and a placebo and did NOT include a proven antidepressant as well.  Other criticisms include a possibility of low expectations on the part of the researchers for both the herb and the placebo; the low expectations may have biased the results.  

A major three-year, multicenter, randomized, double-blind, clinical study sponsored by the National Institutes of Health testing St. John's Wort on its antidepressant effect is underway in the United States. Patients suffering from major depression are receiving either St. John's Wort, Sertraline (Zoloft), or a placebo for eight weeks. The results have not been published. To find out more about the status of these clinical trials go to and enter "St. John's Wort" in the search function. 

Externally, oily preparations are used to treat inflammation of the skin, wounds, and burns. 

How it Works Recent studies have indicated the the antidepressive effect may be due to the herb's ability to inhibit the reuptake of serotonin as well as norepinephrine and/or dopamine.  For a long time, it was assumed that hypericin was the active ingredient in St. John's Wort, however, now it is thought to be hyperforin.  Commercially, St. John's Wort is standardized by hypericin which adds to the overall confusion.  In the final analysis, the herb may work in a variety of ways, none of which account for the overall effect.  

The anti-inflammatory action may be due to the high flavonoid content in the oily preparation. 

Precautions:  Depression and anxiety can be serious conditions.  Consumers contemplating the use of this herb for these conditions should first consult with a health care provider.  Because of the increased effect on serotonin levels this is especially important if an MAO inhibitor or an SSRI has already been prescribed and is being used.  In addition, individuals who are taking a drug that induces photosensitization (e.g., tetracyclines) or who have a history of sensitivity to light should be cautious when using St. John's Wort. While no general health hazards are known if proper administration and dosages are adhered to, central nervous system effects, dermatologic effects, and gastrointestinal effects have been detected in certain individuals.

Daily Dosage:  Capsules are usually standardized at .3% hypericin. Consult a physician or a pharmacist regarding the content of the capsules prior to purchase. For depression, 300 mg of the standardized extract, in capsule form, should be administered 3 times per day (PDR® for Herbal Medicines. 2nd edition).  In general, the duration of the treatment should be 4-6 weeks. As a tea, which is the traditional method of administration, a single dose of 2-3 grams of the dried herb, placed in boiling water, should be used.

Storage:  Store at room temperature.  Keep away from heat, moisture, and direct sunlight.


Parker-Pope, T. (April 27, 2001).  Study debunking use of St. John's Wort is criticized for flaws.  The Wall Street Journal. p. B1.

Philipp, M., Kohnen, R., & Hiller, K-O. (December 11, 1999).  Hypericum extract versus imipramine or placebo in patients with moderate depression:  randomised multicentre study of treatment for eight weeks.  British Medical Journal. Vol. 19, 1534-1539.

PDR® for Herbal Medicines. 2nd edition.  (2000).  Montvale, NJ:  Medical Economics Company.

Shelton, R.C., Keller, M.B., Gelenberg, A., et al. (April 18, 2001).  Effectiveness of St. John's Wort in major depression:  A randomized controlled trial.  The Journal of the American Medical Association. Vol. 285, No. 15, 1978-1986.