St. John's Wort

This is the anchor of the whole evidence base. The 2008 Cochrane review pooled 29 randomised, double-blind trials in 5,489 patients with major depression, finding hypericum extracts superior to placebo and similarly effective to standard antidepressants, with fewer patients discontinuing due to adverse effects ^{1Reference 1Linde et al. · 2008Meta-analysisSt John’s wort for major depression — systematic review, meta-analysisView study →}. Later meta-analyses agree: a 2017 synthesis of 27 trials (3,808 patients) reported response and remission rates statistically comparable to SSRIs with about half the dropout rate ^{2Reference 2Ng et al. · 2017Meta-analysisClinical use of Hypericum perforatum (St John’s wort) in depression: A meta-analysisView study →}, and a 2023 meta-analysis against SSRIs reached the same conclusion on efficacy and tolerability ^{3Reference 3Zhao et al. · 2023Meta-analysisThe efficacy and safety of StView study →}. The effect is anchored to specific hydroalcoholic extracts — hyperforin-standardised WS 5570 at 300 mg three times daily beat placebo on the Hamilton scale in a 375-patient RCT ^{5Reference 5Lecrubier et al. · 2002RCTEfficacy of StView study →} — and a 2025 meta-analysis of milder depression found no significant response difference between St. John’s wort and fluoxetine ^{4Reference 4Urata et al. · 2025Meta-analysisEfficacy of Pharmacological Interventions in Milder Depression: A Systematic Review and Meta-AnalysisView study →}. The important limit: two large US trials in more severe major depression (HAM-D ≥20) found no separation from placebo ^{6,7Reference 6Hypericum Depression Trial Study Group · 2002RCTEffect of Hypericum perforatum (St John’s wort) in major depressive disorder: a randomised controlled trialView study →Reference 7Shelton et al. · 2001RCTEffectiveness of St John’s wort in major depression: a randomised controlled trialView study →}, so the benefit is real but confined to milder illness and to standardised products.

Gap: Trials are dominated by proprietary German extracts; efficacy does not generalise to teas or non-standardised powders, and the herb underperforms in severe major depression.

Two independent placebo-controlled trials used the extract LI 160 in patients with somatoform disorders (bodily symptoms without an organic cause) but not major depression. A 2004 randomised, double-blind study in 184 outpatients (300 mg twice daily, 6 weeks) found the extract superior to placebo across a combined measure of six symptom scales ^{8Reference 8Müller et al. · 2004RCTTreatment of somatoform disorders with StView study →}. An earlier multicentre RCT in 151 outpatients (600 mg/day) likewise showed significant improvement over placebo on somatic anxiety ^{9Reference 9Volz et al. · 2002RCTSt John’s wort extract (LI 160) in somatoform disorders: results of a placebo-controlled trialView study →}. The consistency across two trials from different groups is what lifts this above a single-study signal.

Gap: Both trials are 6 weeks, of modest size, and use the same LI 160 extract; long-term data and independent extracts are absent.

A 2014 meta-analysis concluded that Hypericum perforatum preparations were significantly superior to placebo for menopausal complaints, with an adverse-event rate no higher than placebo ^{10Reference 10Liu et al. · 2014Meta-analysisHypericum perforatum L. preparations for menopause: a meta-analysis of efficacy and safetyView study →}. The signal is muddied by preparation: several of the pooled trials combined St. John’s wort with Vitex agnus-castus, so the effect cannot be cleanly attributed to hypericum alone, and a double-blind pilot of the solo herb (900 mg three times daily) in perimenopausal women found only a non-significant reduction in hot-flash score versus placebo ^{11Reference 11Al-Akoum et al. · 2009RCTEffects of Hypericum perforatum (StView study →}. The most consistent read is a genuine effect on mood and quality-of-life dimensions of the menopausal transition, with weaker, less certain data on hot flashes specifically.

Gap: Best evidence often bundles SJW with other herbs; solo-herb effect on vasomotor symptoms is unconfirmed in adequately powered trials.

Two small randomised, double-blind, placebo-controlled trials test the serotonergic rationale for PMS. A crossover trial in 36 women with mild PMS reported that St. John’s wort improved physical and behavioural symptoms significantly more than placebo, but not mood or pain — a dissociation the authors highlighted ^{12Reference 12Canning et al. · 2010RCTThe efficacy of Hypericum perforatum (St John’s wort) for the treatment of premenstrual syndrome: a randomised, double-blind, placebo-controlled trialView study →}. A second small randomised trial has been published ^{13Reference 13Ghazanfarpour et al. · 2011RCTHypericum perforatum for the treatment of premenstrual syndrome — randomised controlled trialView study →}, though it appears only as a short communication without a retrievable abstract, so its specific results could not be independently confirmed here. Overall the base is small and short, and the split result in the trial that can be verified (some symptom clusters respond, others do not) keeps this in the plausible-but-unproven band.

Gap: Tiny samples, few trials, and inconsistent effects across symptom domains; no large confirmatory RCT.

This is a distinct, traditional use of the infused oil rather than the oral extract. A randomised, double-blind trial in 144 women found that a topical Hypericum perforatum ointment applied three times daily accelerated caesarean wound healing and reduced scar formation versus placebo and no-treatment controls ^{14Reference 14Samadi et al. · 2010RCTThe effect of Hypericum perforatum on the wound healing and scar of caesarean — randomised, double-blind trialView study →}. The signal is not uniform: a 2025 RCT of topical St. John’s wort oil on stage 1–2 pressure injuries found no difference from saline at any weekly timepoint ^{15Reference 15Yıldırım et al. · 2025RCTThe Effects of StView study →}. The mechanism plausibly involves the anti-inflammatory flavonoids and hyperforin’s antibacterial activity, but the clinical data are mixed and wound-type-specific.

Gap: Few trials, different wound types and formulations, and at least one clear null; topical results say nothing about oral use.

This indication rests entirely on the isolated pigment hypericin acting as a photosensitiser under light — photodynamic therapy — not on the ingested herb. In cell and preclinical work, light-activated hypericin generates reactive oxygen species that inhibit proliferation and trigger death across many tumour cell lines including bladder, colon, breast, melanoma and glioma ^{16Reference 16Dong et al. · 2021ReviewHypericin-mediated photodynamic therapy for the treatment of cancer: a reviewView study →}. Separately, hypericin binds the envelope of SARS-CoV-2 and inactivates enveloped viruses, an effect greatly augmented by light ^{17,18Reference 17Delcanale et al. · 2022In vitroThe Interaction of Hypericin with SARS-CoV-2 Reveals a Multimodal Antiviral Activity — in vitroView study →Reference 18Hudson et al. · 1991In vitroAntiviral activities of hypericin — in vitroView study →}. These are genuine, mechanistically detailed findings — but they describe a purified compound plus irradiation, a context far removed from swallowing a depression extract.

Gap: In vitro and photodynamic only; the ingested herb delivers neither the concentrations nor the targeted illumination these effects require. No clinical oncology or antiviral trials of the herb.

The preclinical and human data point in opposite directions. A 2016 meta-analysis of rodent studies concluded that Hypericum perforatum improved cognitive performance across multiple memory paradigms ^{19Reference 19Ben-Eliezer et al. · 2016Meta-analysisHypericum perforatum as a cognitive enhancer in rodents: A meta-analysis (animal model)View study →}. In humans, an acute randomised, double-blind, placebo-controlled trial in 82 healthy adults given 250 or 500 mg found no improvement in short-term memory or sustained attention at either dose ^{20Reference 20Yechiam et al. · 2019RCTThe acute effect of Hypericum perforatum on short-term memory in healthy adults — randomised, double-blind, placebo-controlled trialView study →}. The gap between a positive animal meta-analysis and a null human trial is exactly the pattern that should temper any cognition claim.

Gap: Positive evidence is rodent-only; the one controlled human test was null. No chronic-dosing human cognition trials.

An early 12-week open-label trial in 12 patients (450 mg of 0.3% hypericin twice daily) suggested benefit on the Yale-Brown Obsessive Compulsive Scale ^{22Reference 22Taylor et al. · 2000An open-label trial of StView study →}, which motivated a controlled test. That test was negative: a 12-week double-blind RCT randomised 60 patients to the extract LI 160 or placebo and found no significant difference between them ^{21Reference 21Kobak et al. · 2005RCTSt John’s wort versus placebo in obsessive-compulsive disorder: results from a double-blind study (RCT)View study →}. This is the textbook trajectory of an uncontrolled positive result not surviving blinding.

Gap: The single controlled trial was null; the positive data are uncontrolled. On current evidence St. John’s wort is not supported for OCD.

St. John’s wort is one of the most interaction-prone herbs in common use. Its phloroglucinol hyperforin is a potent activator of the pregnane-X receptor, which induces the drug-metabolising enzyme CYP3A4 and the P-glycoprotein transporter, lowering blood levels of many co-administered drugs ^{25,27Reference 25Nicolussi et al. · 2020ReviewClinical relevance of StView study →Reference 27Hohmann et al. · 2024Dose-dependent induction of CYP3A activity by StView study →}. Documented interactions include immunosuppressants (cyclosporine, tacrolimus), anticoagulants (warfarin), digoxin, certain HIV protease inhibitors, statins and, importantly, hormonal contraceptives — a systematic review found reduced contraceptive efficacy and breakthrough bleeding when the two are combined ^{25,26Reference 25Nicolussi et al. · 2020ReviewClinical relevance of StView study →Reference 26Berry-Bibee et al. · 2016Systematic reviewCo-administration of StView study →}. Because the herb is also serotonergic, combining it with SSRIs or other serotonergic drugs (including triptans, tramadol and MAOIs) risks serotonin syndrome ^{1,2Reference 1Linde et al. · 2008Meta-analysisSt John’s wort for major depression — systematic review, meta-analysisView study →Reference 2Ng et al. · 2017Meta-analysisClinical use of Hypericum perforatum (St John’s wort) in depression: A meta-analysisView study →}. It additionally causes dose-related photosensitivity through its hypericin content, increasing sunburn risk. Enzyme induction builds over about a week and persists for a week or more after the herb is stopped, which matters when timing new prescriptions or procedures ^{25Reference 25Nicolussi et al. · 2020ReviewClinical relevance of StView study →}. Anyone on prescription medication should consult a clinician before use.