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St. John's Wort — Frequently Asked Questions

Reviewed by·PharmD, BCPS

This content is for informational purposes only and does not constitute medical advice. Consult your healthcare provider before starting any supplement. Full disclaimer

Frequently Asked Questions

Is St. John's Wort as effective as prescription antidepressants?

For mild-to-moderate depression, yes. The Cochrane Collaboration analyzed 29 clinical trials and concluded St. John's Wort matches standard antidepressants (SSRIs) in efficacy for this severity range, with fewer side effects and lower dropout rates. A direct head-to-head trial showed it matched citalopram (Celexa). However, for severe major depression, St. John's Wort has not been shown to be effective — pharmaceutical antidepressants are needed. It is a legitimate treatment option for mild-to-moderate depression, not a general replacement for all antidepressant therapy.

Can I take St. John's Wort with my antidepressant?

Absolutely not. Combining St. John's Wort with SSRIs (sertraline, fluoxetine, escitalopram), SNRIs (venlafaxine, duloxetine), MAOIs, or tricyclic antidepressants creates serious risk of serotonin syndrome — a potentially fatal condition causing high fever, seizures, muscle rigidity, and rapid heart rate. If you want to switch from an antidepressant to St. John's Wort (or vice versa), you must work with your physician and allow a 2-week washout period between stopping one and starting the other.

Why does St. John's Wort interact with so many drugs?

St. John's Wort powerfully induces (speeds up) two major drug-clearing systems in your body: the CYP3A4 enzyme and the P-glycoprotein transporter. Together, these systems metabolize or transport roughly 50% of all prescription drugs. When St. John's Wort activates them, your body clears these drugs faster, dropping their blood levels below therapeutic range. This is why it interacts with such a wide range of medications — from birth control pills to HIV drugs to blood thinners to immunosuppressants.

Does St. John's Wort affect birth control pills?

Yes — this is one of the most important interactions. St. John's Wort induces CYP3A4, which metabolizes the hormones in oral contraceptives faster than normal, reducing their blood levels. Documented consequences include breakthrough bleeding and unplanned pregnancies. If you take oral contraceptives and want to use St. John's Wort, use an additional barrier contraception method (condoms) while taking SJW and for at least one month after stopping.

How long does St. John's Wort take to work?

Like pharmaceutical antidepressants, St. John's Wort requires 2-4 weeks for initial mood improvement and 4-6 weeks for full therapeutic effect. This is because the neurotransmitter changes need time to downstream-regulate receptor sensitivity and gene expression. Do not judge its effectiveness before 4 weeks at the full 900mg daily dose. If no improvement after 6 weeks, it may not be effective for your specific situation.

Is St. John's Wort safe for anxiety?

Emerging evidence suggests it helps with anxiety, particularly as a secondary benefit in patients with comorbid depression and anxiety. One small RCT showed significant improvement in social anxiety disorder. However, the evidence base for anxiety alone is much smaller than for depression. If anxiety is your primary concern and you don't take medications that interact with SJW, it is a reasonable option to try under healthcare provider guidance. Standard dose is 900mg/day for 4-6 weeks.

Can St. John's Wort cause sun sensitivity?

Yes. Hypericin, one of the active compounds, is a photosensitizer that increases skin sensitivity to UV radiation. At standard supplemental doses (900mg/day), the risk is modest but real — particularly for fair-skinned individuals. Apply broad-spectrum sunscreen (SPF 30+) daily, wear protective clothing, and avoid prolonged sun exposure or tanning beds while taking St. John's Wort. The risk increases at higher doses (1,200-1,800mg/day).

Should I tell my doctor I am taking St. John's Wort?

Absolutely — this is critical. St. John's Wort interacts with more medications than almost any other supplement. Your physician and pharmacist need to know about SJW use to check for dangerous interactions with any current or newly prescribed medications. This includes before any surgery (anesthesia interactions exist), before starting any new prescription, and especially before starting any antidepressant, blood thinner, contraceptive, or immunosuppressant. Treat St. John's Wort as you would any prescribed medication for disclosure purposes.

Full St. John's Wort Guide

References

  1. Linde K, Berner MM, Kriston L (2008). St John's wort for major depression. Cochrane Database of Systematic Reviews. DOI PubMed
  2. Gastpar M, Singer A, Zeller K (2006). Comparative efficacy and safety of a once-daily dosage of hypericum extract STW3-VI and citalopram in patients with moderate depression: a double-blind, randomised, multicentre, placebo-controlled study. Pharmacopsychiatry. DOI PubMed
  3. Moore LB, Goodwin B, Jones SA, Wisely GB, Serabjit-Singh CJ, Willson TM, Collins JL, Kliewer SA (2000). St. John's wort induces hepatic drug metabolism through activation of the pregnane X receptor. Proceedings of the National Academy of Sciences. DOI PubMed
  4. Muller WE, Singer A, Wonnemann M, Hafner U, Rolli M, Schafer C (1998). Hyperforin represents the neurotransmitter reuptake inhibiting constituent of hypericum extract. Pharmacopsychiatry. DOI PubMed
  5. Kobak KA, Taylor LV, Bystritsky A, Kohlenberg CJ, Greist JH, Tucker P, Warner G, Futterer R, Vapnik T (2005). St John's wort versus placebo in social phobia: results from a placebo-controlled pilot study. Journal of Clinical Psychopharmacology. DOI PubMed
  6. Rahimi R, Nikfar S, Abdollahi M (2009). Efficacy and tolerability of Hypericum perforatum in major depressive disorder in comparison with selective serotonin reuptake inhibitors: a meta-analysis. Progress in Neuro-Psychopharmacology and Biological Psychiatry. DOI PubMed