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ST. JOHN’S WORT (Hypericum perforatum)

Complementary/ alternative medicine.

Available in a range of herbal remedies available from pharmacies and health food shops.

Effective in the treatment of mild to moderate depression (1)
No more effective than placebo in the treatment of severe depression (2)(3)

St. John’s Wort has the potential to affect the metabolism of other medications including oral contraceptives, hormone replacement therapy (HRT), and SSRIs through CYP450 3A4 (4). There have been case reports of women becoming pregnant when taking St. John’s Wort while on oral contraception. (5)


Use in Pregnancy

•    There are very few studies which examine the effects of St. John’s Wort during pregnancy
•    A recent prospective study examined the effects of St. John’s Wort in 54 women taking it during their pregnancy, compared to a control group of pregnant women not taking it. There were no significant differences in rates of major malformations, live births and prematurity rates between those exposed and non exposed to St. John’s Wort. (6)
•    Animal studies have found that use of hypericum perforatum in rats at the equivalent dose to that used in humans resulted in some damage to kidneys and liver (7)


Use in Breast Feeding

•    There is very little data on the safety of St. John’s Wort in breastfeeding.
•    One small study of 33 patients using St. John’s Wort while breastfeeding found that there was a higher incidence of babies with colic (2 babies), drowsiness (2 babies) and lethargy (1 baby) among mothers taking the medication compared with controls. The study numbers were too small however to be able to make any strong conclusions either way on its safety (8).
•    A smaller study of 5 women using St. John’s Wort while breastfeeding indicated that levels of St. John’s Wort excreted in breast milk are low ranging from 0.9 to 2.5% relative dose. This is comparable to levels of antidepressants reported in studies. (9)
•    Animal studies found severe damage to the liver and kidneys of rats that had been exposed to hypericum perforatum doses equivalent to that used in humans for 21 days through breastfeeding (7).


(1)    Lecrubier, Y.et al (2002). Efficacy of St. John's Wort extract WS 5570 in major depression: a double-blind, placebo-controlled trial. Am. J. Psychiatry 159 (8), 1361–1366.
(2)    Shelton, R.C., et al (2001). Effectiveness of St. John's Wort in major depression: a randomized controlled trial. JAMA 285 (15), 197886.
(3)    Davidson, J.R., et al, (Hypericum Depression Trial Study Group), (2002). Effect of Hypericum perforatum (St John’s Wort) in major depressive disorder: a randomized controlled trial. JAMA 287, 1807–1814.
(4)    Freeman M. (2009). Complementary and alternative medicine for perinatal depression.  Journal of Affective Disorders. 112: 1-10
(5)    Schwartz et al (2003). Unwanted pregnancy on self-medication with St John’s Wort despite hormonal contraception. Br J Clinical Pharmacol: 55, 112–113
(6)    Moretti M. et al (2009) Evaluating the safety of St. John’s Wort in human pregnancy. Reproductive Toxicology 28 (2009) 96–99
(7)    Gregoretti B. et al. (2004) Toxicity of Hypericum perforatum (St. John’s Wort) administered during pregnancy and lactation in rats. Toxicology and Applied Pharmacology. 200: 201–205
(8)    Klier C. et al. (2006) St. John’s Wort (Hypericum perforatum) and breastfeeding: plasma and breast milk concentrations of hyperforin for 5 mothers and 2 infants. J Clin Psychiatry;67:305-309
(9)    Lee A. et al (2003). The Safety of St. John’s Wort (Hypericum perforatum) During Breastfeeding. J Clin Psychiatry;64:966–968

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