St John’s Wort for Anxiety and Depression

The exact mechanism of how St John’s wort (Hypericum perforatum) works on depression is unknown. The extract of this plant itself contains at least 10 different substances and scientists are not exactly sure which one works for depression and at what combination ratios. It is thought that St. John’s Wort extract prevents the breakdown of the neurotransmitters serotonin, norepinephrine, and dopamine. All of these neurotransmitters are necessary for a balanced and normal mood. In theory, St. John’s Wort increases the level of serotonin.



“The present results, together with previous pharmacological and phytochemical data, indicated that Hypericum grandifolium possess antidepressant-like effects in mice and that different constituents, such as the flavonoids and the benzophenone derivatives, could be responsible at least in part for the antidepressant effects observed for this species.” (J Ethnopharmacol. 2009 Jan 21;121(2):297-303. Epub 2008 Nov 8.)

“St John’s wort (as used in this study) can be at least as effective as paroxetine in acute treatment of moderate to severe depression among adults in the short-term.” (Can Fam Physician. 2007 September; 53(9): 1511–1513. PMCID: PMC2234633)

Dosage and Sources:

St. Johns wort is sold as food supplements and is available in health shops. The typical dose to combat depression is 300 mg taken 3 times daily.



1. John’s Wort for depression (Cochrane review). In: The Cochrane Library, Issue 3, 2004. Wiley, Chichester, UK.[PubMed]
2. National Institute for Clinical Excellence. Depression: management of depression in primary and secondary care. December 2004. NICE clinical guideline 23. Available at (accessed on 30 September 2008).
3. National Center for Complementary and Alternative Medicine. St. John’s Wort. 2001 July 2005. NCCAM Publication No. D269. Available at (accessed on 9 October 2007).
4. John’s wort in major depression: a randomized controlled trial. Journal of the American Medical Association. 2001; 285: 1978-1986.[PubMed]
5. Hammerness P, Basch E, Ulbricht C, et al. St John’s wort: a systematic review of adverse effects and drug interactions for the consultation psychiatrist. Psychosomatics. 2003; 44: 271-282.[PubMed]

Last Update:  January 17, 2009

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