Pharmacognosy · Mental Health · Real Drug Interactions

St. John's Wort

Hypericum perforatum L. — a sun-loving perennial herb traditionally gathered around the feast of St. John — among the most rigorously studied herbal antidepressants, with genuine clinical efficacy for mild-to-moderate depression matched by an equally genuine and clinically serious list of drug interactions.

56 Primary Refs
17 Properties
Flower Parts Used
✦ Researched
Last Updated
Primary Source Wikiphyto · NCBI PubMed · UK MHRA
Family Clusiaceae
Mental Health · Extensive Drug-Interaction Profile

Biological Overview

St. John's Wort is a perennial herb of Eurasian origin, growing up to 80 cm, with an erect, angular, branching stem. Its oval, opposite leaves are dotted with black marks along the edges and covered in tiny translucent glands that look like little perforations when held up to the light — the source of its species name.

Life CyclePerennial herb, up to 80 cm
HabitatEurasia; cultivated worldwide
Trials in Major Meta-Analysis27 trials, 1,757 patients
Marker CompoundsHypericin, Hyperforin
Botanical Classification

Taxonomy & Identification

Latin Name
Hypericum perforatum L.
Family
Clusiaceae (= Guttiferaceae = Hypericaceae)
Common Names
St. John's Wort, Perforate St John's-wort
Parts Used
Flowering tops, harvested in summer
Habitat
Eurasian native, now widely cultivated
From Sun Cults to Modern Trials

History & Tradition

One of the flowers traditionally associated with the feast of St. John, this plant was used to prepare "Baume Tranquille" and, more recently, "Baume du Commandeur," valued for its wound-healing properties; in the Middle Ages it was also used to treat cases of dementia.

It became linked to solar cults for two reasons: its flowering coincides with the feast of St. John near the summer solstice, and the oil macerate of its flowers turns a vivid red after weeks of light exposure. Its antidepressant properties were not described until the 1960s in Germany, where it was subsequently the subject of extensive pharmacological and clinical study.

⚠ Read This Before Combining With Any Medication

St. John's Wort has one of the longest and most clinically significant drug-interaction profiles of any herb on this site. If you take any prescription medication, read Safety & Drug Interactions in full before starting.

Timeline

Medieval Era

Wound Balm & "Dementia" Treatment

Used in vulnerary balms and, in the Middle Ages, for cases described at the time as dementia.

1960s

Antidepressant Properties Discovered

German researchers begin extensive pharmacological and clinical study of its antidepressant activity.

1996

Landmark Meta-Analysis

A meta-analysis of 27 trials (1,757 patients) finds it more effective than placebo and as effective as low-dose tricyclic antidepressants.[3]

2014

UK Contraceptive Safety Alert

The UK's MHRA issues a formal alert after 19 suspected interactions with hormonal contraceptives, including 15 unplanned pregnancies.[48]

The Key Molecules

Hyperforin & Hypericin — Deep Dive

Two compound families, working in synergy — and the same mechanism behind both the plant's antidepressant effect and its drug interactions.

🎯

Hyperforin — The Leading Candidate

A phloroglucinol derivative, likely the strongest individual candidate for the antidepressant effect, inhibiting reuptake of serotonin, dopamine, and noradrenaline with similar affinity.[6]

🔴

Hypericin — The Red Pigment

A naphthodianthrone pigment, mildly serotonergic and melatoninergic, and the compound responsible for the plant's signature deep red oil macerate.

🧬

Genuine Pharmacological Synergy

Numerous compounds act synergistically through two complementary mechanisms: shared-target pharmacodynamic synergy (hypericin, flavonols, and xanthones all inhibit MAO and COMT) and pharmacokinetic synergy (procyanidin increases the water solubility, and therefore bioavailability, of the naphthodianthrones).[16][11][12]

⚗️

The Same Compound Drives the Interactions

Hyperforin content is significantly correlated with the degree of CYP3A4 enzyme induction — meaning the same compound credited with much of the antidepressant effect is also the main driver of the plant's drug interactions.[49]

⚠ Low-Hyperforin Extracts May Carry Less Interaction Risk

Not all St. John's Wort extracts behave the same way pharmacologically.

A low-hyperforin Hypericum extract was tested in 20 healthy volunteers receiving a drug cocktail, and no pharmacokinetic interaction was observed across CYP1A2, CYP2B6, CYP2C9, CYP2C19, CYP3A4, or P-glycoprotein.[50] This is a promising finding, but it does not change the safety guidance below for standard, higher-hyperforin extracts — confirm the extract type with a healthcare provider before combining with any medication.

Available Forms

Parts Used & Available Forms

The flowering tops, prepared in five documented galenic forms.

Mother Tincture

An alcoholic tincture of the whole plant.

Liquid · Traditional

Standardized Dry Extract

A hydroalcoholic dry extract standardized to hypericin and/or hyperforin (the most active fraction) — the form used in nearly all major clinical trials.

Standardized · Clinical Trial Form

EPS (Standardized Plant Extract)

A standardized fresh-plant extract of the whole flowering plant.

Fresh Plant Extract

Fluid Extract

A concentrated liquid extract of the flowering tops.

Liquid Extract

Oil Macerate

Flowers macerated in olive oil for three weeks in sunlight, turning a deep red color — used externally for burns and sunburn. This form is photosensitizing and should not be applied before sun exposure.

External Use Only

Clinical Dosimetry

Dosages

A consistent standardized dose, with detailed equivalents across preparation types.

Form Dose Equivalent
Standardized Dry Extract 600 mg/day, standardized to 0.2–0.3% hypericin 2–4 g of crude drug; 0.2–1 mg hypericin
Formulated Capsules/Tablets 600–900 mg/day 200–300 mg per capsule, ratio 4–7:1 dried flowering top to extract
Mother Tincture 3× 20 drops/day (3 mL total) ~0.15 mg hypericin/day (tincture averages 5 mg hypericin per 100 mL)
General Dosing Pattern 2–3 doses/day 1–3 mg total hypericin/day maximum; minimum effective dose ~0.6–1 mg/day

No positive effect should be expected before 10 to 14 days of treatment. If no effect has appeared after 4 to 6 weeks, treatment should be discontinued. Clinical experience suggests efficacy is more pronounced in winter-pattern depression, possibly related to melatonin. Confirm dosing with a healthcare provider, and review Safety & Drug Interactions before combining with any other medication.

Phytochemistry

Composition

A genuinely diverse chemical profile, with melatonin among its more unexpected constituents.

Naphthodianthrones & Phloroglucinols

Hypericin & Related Pigments0.06–0.15%; pseudohypericin, isopseudohypericin, protopseudohypericin, cyclopseudohypericin
Major
Hyperforin & Adhyperforin2–5%; phloroglucinol-derived, prenylated compounds
Major
HydroperoxycadiforineConsidered the best candidate for the antidepressant effect alongside hyperforin
Present
Essential Oiln-alkanes and monoterpenes, including alpha-pinene, beta-pinene, limonene, and caryophyllene[2]
Trace

Flavonoids & Other Constituents

Hyperoside, Isoquercitroside, Rutoside, QuercetolFlavonoids
Present
Biapigenin & AmentoflavoneBiflavonoids (0.1–0.5%); amentoflavone binds benzodiazepine receptors
Present
Tannins & ProanthocyanidolsProcyanidin increases naphthodianthrone bioavailability
Present
Melatonin4,490 ng/g — an unusually direct dietary source of melatonin[1]
Present

Plant Properties — Pharmacodynamics

17 properties documented, anchored by one of the deepest antidepressant evidence bases of any herb.

17 Properties Antidepressant Anxiolytic Neuroprotective
😌

Antidepressant

Activity linked to reuptake inhibition of neuromediators — mainly serotonin, also dopamine and noradrenaline — and moderate interaction with GABA-A receptors, mainly via hyperforin.[3][4][6][7][8][9][10]

🧘

Anxiolytic

Documented anxiolytic activity in animal models, including normalizing restraint-stress-induced behavioral and biochemical alterations in mice.[13][14][23]

😴

Sedative

Documented sedative activity, including with extracts free of hyperforin.[15]

🧫

MAO & COMT Inhibition

Hydroalcoholic extracts selectively inhibit monoamine oxidase type A (MAO) via flavonoids and xanthones, and inhibit catechol-O-methyltransferase (COMT).[17]

🦠

Antiviral (Hypericin)

Hypericin may act against cytomegalovirus (CMV) and herpes simplex.[18]

🔬

Photodynamic Anticancer Potential

Hypericin is a potent natural photosensitizer applicable to photodynamic therapy for various oncological diseases, including potential photodetection of ovarian cancer micrometastases.[19]

🧠

Neuroprotective

Documented neuroprotective activity for the plant and its major components.[20]

🎗️

Tumor Growth Inhibition

Hyperoside acts on human brain tumors; hyperforin inhibits tumor growth in leukemic and glioblastoma cells, synergistically with hypericin and procyanidin B2, via caspase activation and apoptosis induction.[21]

🌙

Serotoninergic & Melatoninergic

Increases melatonin levels in the body.[22]

🔥

Anti-Inflammatory & Analgesic

Documented anti-inflammatory and pain-relieving activity.[24]

🛡️

Gastric Protection (Oil Macerate)

Documented gastric protective activity for the oil macerate.[25]

🍽️

Cholagogue & Digestive

Traditionally used to stimulate bile flow and support digestion.

🩹

External Use: Wound Healing

Antiseptic, astringent, healing, and vulnerary properties, mainly as an oil macerate.[26]

☀️

Mild Sun Protection (Oil Macerate)

Too weak on its own to protect skin against UVB, but useful in combination with UVB filters to protect skin during the first days of sun exposure.[27]

🦷

Periodontal Disease Support

Usable in inflammatory periodontal disease, inhibiting plasma extravasation and decreasing bone resorption.[28]

🌬️

Essential Oil
Anti-Inflammatory & Anti-Angiogenic

The essential oil shows anti-inflammatory activity and potential anti-angiogenic properties, demonstrated using the chorioallantoic membrane assay.[30]

🌿

Related Species
Antimalarial (H. lanceolatum)

A related species, Hypericum lanceolatum, has documented antimalarial properties — distinct from H. perforatum itself.[29]

Clinical Applications

Clinical Indications

An unusually well-documented indication, anchored by repeated head-to-head trials against standard antidepressants.

😌
Mild-to-Moderate Depression
Primary, Best-Studied Indication
  • Depressive states (mild to moderate), especially seasonal depression and depression linked to nervous fatigue or physiological states such as menopause.
  • A 1996 meta-analysis of 27 trials (1,757 patients total) found it more effective than placebo and as effective as low-dose tricyclic antidepressants, a finding echoed in a subsequent Cochrane review. [3][31]
  • A 324-patient double-blind trial using a 0.2% hypericin-standardized alcoholic extract showed identical efficacy to 50 mg of imipramine twice daily; another study found the same efficacy with better tolerability. [32][33]
  • Comparable efficacy to SSRIs in a meta-analysis. [34]
  • Significant reduction in Hamilton depression scores compared with paroxetine, with better severity-score improvement and better medium-term remission. [35]
  • Good efficacy and tolerability confirmed in further review. [36]
🧠
Broader Mental Health Uses
Less Established
  • Post-traumatic stress, ADHD, OCD, and anxiety disorders are discussed in the literature. [37]
  • A combination extract (with oat, passionflower, and lavender) significantly reduced morphine withdrawal symptoms in rats. [38]
⏱️
Practical Treatment Guidance
From Clinical Experience
  • No positive effect should be expected before 10–14 days of treatment.
  • Discontinue if no effect appears after 4–6 weeks.
  • Efficacy appears more pronounced in winter-pattern depression, possibly related to melatonin activity.
🩹
External Use
Oil Macerate Only
  • Wounds, burns, and sunburn — applied as an oil macerate, never before sun exposure due to its photosensitizing effect.
Pharmacodynamics

Mode of Action

A genuinely multi-target mechanism, attributed to synergy between several compound families rather than one single active ingredient.

🧬

Naphthodianthrone–Phloroglucinol–Flavonoid Synergy

Pharmacological activity appears attributable to synergy between the naphthodianthrones (hypericin), the phloroglucinol derivatives (hyperforin), and various flavonoids, rather than to any single compound.[39]

🟡

Kielcorine — A Possible Additional Active Principle

Kielcorine, a xanthone, may be one of the active principles, alongside the plant's role as a natural source of melatonin.

🎯

Synaptosomal Reuptake Inhibition

The primary documented mechanism: inhibition of synaptosomal reuptake of serotonin, dopamine, and noradrenaline (norepinephrine), with similar affinity for all three.

🔬

Broader Receptor Activity

Modulates glutamate and acetylcholine neurotransmission; shows in vitro affinity for adenosine, GABA(A), GABA(B), and glutamate receptors; and in vivo, decreases beta-adrenergic receptor activity while increasing serotonin activity.[37]

Clinical Safety

Safety & Drug Interactions

Generally safe on its own. The real risk is what it does to other medications.

☀️

Direct Adverse Effects

  • Photosensitizing, by inducing singlet oxygen formation — sun exposure caution is warranted, particularly at higher doses.
  • Serotonin syndrome: a few cases reported in elderly patients combining an SSRI antidepressant with St. John's Wort.
  • Good general safety profile otherwise, per toxicological and systematic review.[51][5]
  • Essential oil may be allergenic.
⚙️

The Mechanism Behind the Interactions

  • Enzyme induction: St. John's Wort induces CYP3A4 (mainly via hyperforin) and P-glycoprotein (mainly via hypericin), speeding up the elimination of many drugs.[42][46][47]
  • Reduced drug effect: faster elimination can lower the plasma concentration of the affected medication, possibly via CYP2C9, CYP3A4, and CYP1A2 induction (though some sources find no effect on CYP2C9, CYP1A2, or CYP2D6).[43][44][45]
  • Stopping abruptly matters too: suddenly discontinuing St. John's Wort can cause the plasma concentration of the interacting medication to rise, increasing its toxicity risk.

Documented Drug Interactions by Category

Category Medications
Hormonal Contraceptives Combined pills, progesterone-only pills, etonogestrel implants — reduced effectiveness; UK MHRA documented 15 unplanned pregnancies from 19 suspected interactions (2000–2014)[48]
Anticoagulants Vitamin K antagonists (warfarin, phenprocoumon)
Immunosuppressants Cyclosporine, tacrolimus — relevant for transplant patients especially
HIV Medications Indinavir and other protease/reverse transcriptase inhibitors — documented reduced indinavir concentrations[41]
Cardiac Medications Digoxin
Respiratory Theophylline
Antidepressants SSRIs, amitriptyline — risk of serotonin syndrome when combined
Other Fexofenadine, methadone, midazolam, nevirapine, simvastatin, irinotecan, imatinib[40]
Clinical Disclaimer: This monograph is for educational and professional reference only. It does not constitute medical advice, diagnosis, or treatment guidance. St. John's Wort has one of the most clinically significant drug-interaction profiles of any commonly used herbal supplement. Always consult a qualified healthcare provider before starting it if you take any prescription medication — especially hormonal contraceptives, anticoagulants, immunosuppressants, HIV medications, or other antidepressants — and never stop taking it abruptly without medical guidance if you are on an interacting medication.
Common Questions

Frequently Asked Questions

Does St. John's Wort actually work for depression?
The evidence is unusually strong for an herbal supplement. A 1996 meta-analysis of 27 trials covering 1,757 patients found it more effective than placebo and as effective as low-dose tricyclic antidepressants. Multiple later trials found it comparably effective to standard SSRIs like paroxetine, sometimes with better tolerability. It is specifically studied for mild-to-moderate depression, not severe depression.
Why is St. John's Wort dangerous to combine with other medications?
St. John's Wort induces the CYP3A4 liver enzyme and P-glycoprotein, which speeds up the breakdown of many drugs and can make them significantly less effective. This is a well-documented mechanism affecting a long list of medications, including hormonal contraceptives, blood thinners like warfarin, immunosuppressants like cyclosporine and tacrolimus, certain HIV medications, and other antidepressants. Stopping St. John's Wort abruptly can also cause levels of these other drugs to rise suddenly.
Can St. John's Wort make birth control fail?
Yes, this is a real and specifically documented risk. The UK's Medicines and Healthcare products Regulatory Agency issued a safety alert in 2014 after 19 suspected interactions were reported between 2000 and 2014, including 15 unplanned pregnancies linked to combining St. John's Wort with hormonal contraceptives.
What is the recommended dose of St. John's Wort?
The standard dose is 600 mg per day of a dry extract standardized to 0.2 to 0.3% hypericin, sometimes up to 900 mg per day, typically split into 2 to 3 doses. It generally takes 10 to 14 days before any positive effect appears, and treatment should be discontinued if no effect is seen after 4 to 6 weeks.
How does St. John's Wort work for depression?
Its activity is attributed to a synergy between several compound families rather than one single active ingredient: hyperforin (likely the strongest individual candidate, inhibiting reuptake of serotonin and other neurotransmitters), hypericin (mildly serotonergic and melatoninergic), and various flavonoids. It modulates serotonin, dopamine, and noradrenaline reuptake with similar mechanisms to conventional antidepressants.
Why does St. John's Wort cause sun sensitivity?
Hypericin and related naphthodianthrone compounds are natural photosensitizers, meaning they can make skin more reactive to sunlight by inducing the formation of singlet oxygen. This is the same property that turns St. John's Wort oil macerate a deep red color after weeks of sun exposure, and it is the basis of the plant's traditional use for burns and sunburn applied externally, paradoxically.
Is St. John's Wort safe to take with antidepressants?
This combination should not be attempted without medical supervision. Cases of serotonin syndrome, a potentially serious condition, have been reported in older patients combining St. John's Wort with SSRI antidepressants. Combining herbal and conventional antidepressants should always involve a healthcare provider.
Primary Literature

Bibliography

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↑ 48. Medicines and Healthcare products Regulatory Agency (MHRA). St John's wort: interaction with hormonal contraceptives, including implants. Published 12 March 2014. MHRA Drug Safety Update →
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Additional Reference Literature

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