St. John's Wort

botanicalSt. John's wort extract

What is it

St. John's wort (Hypericum perforatum) is a flowering plant native to Europe whose aerial parts (flowers and leaves) have been used medicinally for centuries. It is one of the most studied herbal supplements, primarily for mild to moderate depression. The plant gets its name from blooming around the feast day of St. John the Baptist (June 24).

How it works

St. John's wort contains numerous bioactive compounds, with hypericin, pseudohypericin, and hyperforin most studied. Hyperforin is now considered the primary contributor to antidepressant effects, acting through inhibition of monoamine reuptake (serotonin, norepinephrine, dopamine) at the synaptic level. Hypericin contributes the characteristic red pigment and has additional pharmacological activities. Unlike SSRIs, hyperforin works by altering the sodium gradient that drives reuptake transporters, producing a broad-spectrum effect on multiple monoamine neurotransmitter systems. St. John's wort also affects GABA, glutamate, and other neurotransmitter systems, contributing to its complex pharmacology. Effects on mood typically emerge over 2 to 6 weeks of consistent use, similar to prescription antidepressants. Hyperforin is also a potent inducer of cytochrome P450 enzymes (especially CYP3A4) and P-glycoprotein, which underlies St. John's wort's many clinically significant drug interactions. This induction increases the metabolism of many medications, potentially reducing their effectiveness.

Evidence for 6 uses

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Mild to moderate depression

Grade A

Strong evidence

Multiple meta-analyses and systematic reviews of randomized controlled trials show St. John's wort is more effective than placebo and similar to standard antidepressants for mild to moderate depression, with fewer side effects.

Seasonal affective disorder (SAD)

Grade C

Moderate evidence

Some small trials suggest benefit for seasonal depression. Often combined with light therapy.

Menopausal symptoms (mood-related)

Grade C

Moderate evidence

Some trials show possible modest benefit for menopausal mood symptoms and hot flashes, often in combination products.

Severe depression

Grade D

Mixed evidence

Evidence is much weaker for severe depression. Standard prescription antidepressants under specialist care are recommended for severe presentations.

Anxiety

Grade D

Mixed evidence

Limited and mixed evidence for use in primary anxiety disorders. May help anxiety when comorbid with depression.

Somatoform disorders

Grade D

Mixed evidence

Limited evidence suggests possible benefit for some somatoform symptoms in small trials.

4 commercial forms

Standardized extract (0.3% hypericin)

Most common clinical-trial standardization

Standardized to hypericin content. Used in many European and North American depression trials.

Standardized extract (3-5% hyperforin)

Standardized to current understanding of active compound

Hyperforin is now considered the primary antidepressant compound. Some newer products use this standardization.

Dried herb (whole flower/leaf)

Variable potency

Used in teas and traditional preparations. Inconsistent compound content.

Liquid extract / tincture

Alcohol-based extraction

Concentrated form, used in traditional and herbalist applications.

Dosage

There is no established RDA. Clinical trials for depression have typically used standardized extracts (often 0.3 percent hypericin or 3 to 5 percent hyperforin) at 300 mg three times daily (total 900 mg/day). Some trials have used 600 to 1,800 mg per day. Effects on depression require 2 to 6 weeks of consistent use to assess.

When and how to take it

St. John's wort is typically taken three times daily with meals to reduce gastrointestinal effects and maintain steady plasma levels. Effects on mood emerge gradually over 2 to 6 weeks. Use sunscreen and avoid prolonged sun exposure due to potential photosensitivity. Do not stop abruptly if you have been on a high dose for a long time; consider tapering. Inform any new healthcare provider that you are taking St. John's wort because of its many drug interactions.

Safety

St. John's wort is generally well tolerated. The most common side effects are gastrointestinal upset, fatigue, dry mouth, dizziness, headache, restlessness, and photosensitivity. Photosensitivity can be significant at higher doses, especially in fair-skinned individuals. Mania and hypomania have been reported, particularly in people with undiagnosed bipolar disorder. There is no established Tolerable Upper Intake Level.

Who should be cautious

Avoid St. John's wort if you are pregnant, breastfeeding, or take any prescription medication without first consulting a pharmacist or physician. Avoid in people with bipolar disorder (may trigger mania), schizophrenia, or those on antidepressants, oral contraceptives, anticoagulants, immunosuppressants, antiretrovirals, or chemotherapy. Discontinue at least one to two weeks before scheduled surgery (interacts with anesthetics). Not appropriate for severe depression without specialist supervision.

Interactions

St. John's wort has many serious drug interactions, primarily through induction of CYP3A4 and P-glycoprotein. Reduces effectiveness of oral contraceptives (potential unintended pregnancy), warfarin, cyclosporine, tacrolimus, certain antiretrovirals, anticonvulsants, digoxin, statins, certain chemotherapy drugs, and many others. Can cause serotonin syndrome when combined with SSRIs, SNRIs, MAO inhibitors, tramadol, triptans, or other serotonergic drugs. Always discuss with a pharmacist or physician before starting.

Frequently asked questions

Is St. John's wort as good as prescription antidepressants?⌄

For mild to moderate depression, meta-analyses show similar efficacy with fewer side effects. For severe depression, prescription medications under medical supervision are recommended. St. John's wort is not appropriate as DIY treatment for serious depression.

Can I take St. John's wort with my birth control pills?⌄

No. St. John's wort significantly reduces the effectiveness of oral contraceptives, potentially leading to unintended pregnancy. Use additional contraception or choose a different supplement.

Does St. John's wort interact with other medications?⌄

Yes, extensively. It induces liver enzymes that metabolize many medications, reducing effectiveness of drugs including warfarin, immunosuppressants, antiretrovirals, certain chemotherapy drugs, and many others. Always check with a pharmacist or physician before combining.

How long until St. John's wort works?⌄

Effects on mood typically emerge over 2 to 6 weeks of consistent daily use, similar to prescription antidepressants.

Can St. John's wort cause sunburn?⌄

Yes. Hypericin causes photosensitivity. Use sunscreen and avoid prolonged sun exposure, especially at higher doses and in fair-skinned individuals.

References

ChEBI: St. John's wort extract — ChEBI Database link
Wikidata: Hypericum perforatum — Wikidata link

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Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you're pregnant, breastfeeding, on medications, or managing a chronic condition.