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St. John's Wort (Hypericum perforatum)

Hypericum perforatum
Evidence Level
Strong
2 Clinical Trials
4 Documented Benefits
4/5 Evidence Score

St. John's Wort is a flowering plant with over 2,000 years of medicinal use and one of the most extensively studied herbal antidepressants. Its active compounds hypericin and hyperforin have demonstrated antidepressant effects comparable to standard pharmaceutical antidepressants in multiple meta-analyses — with a significantly better tolerability profile for mild to moderate depression. However, it is also among the most clinically significant herbal medicines for drug interactions, inducing CYP3A4 and P-glycoprotein to reduce blood levels of many commonly prescribed medications.

Studied Dose 300 mg three times daily (900 mg/day) standardized to 0.3% hypericin; some extracts standardized to 3–5% hyperforin; 4–6 weeks for full antidepressant effect
Active Compound Hypericin (0.3% standardized) and hyperforin (3–5% standardized) — Jarsin® 300 (Lichtwer Pharma) and LI 160 are the most clinically studied extracts

Benefits

Mild to moderate depression treatment

The most comprehensive meta-analysis of St. John's Wort (29 RCTs, 5,489 patients) confirms it is significantly more effective than placebo and similarly effective to standard antidepressants (SSRIs, TCAs) for mild-to-moderate depression — with significantly fewer side effects and better tolerability. Particularly well-established in European clinical practice where it is licensed as a pharmaceutical in several countries. Evidence is strongest for mild-to-moderate presentations: the large US trial (Davidson 2002, JAMA, n=340) found no benefit over placebo in more severe major depression, so it should not be relied on for severe depression.

Supported by Trial 1

Anxiety and stress reduction

Beyond depression, SJW is sometimes used to help ease everyday anxiety, irritability, and psychological stress. This is a separate and more limited area of evidence than the depression research and is not established by the meta-analyses cited here. The mechanism involves GABAergic modulation and serotonin reuptake inhibition, producing calming effects that complement the antidepressant activity.

Supported by Trial 1

Seasonal affective disorder (SAD)

St. John's Wort has been studied for seasonal affective disorder (winter low mood), with a trial reporting effects comparable to light therapy. This is a separate, limited area of evidence and is not established by the meta-analyses cited here; anyone with seasonal depression should work with a clinician rather than self-treat.

Supported by Trial 2, Trial 1

Menopausal mood symptoms

Some studies in perimenopausal and menopausal women have looked at SJW for mood, irritability, and quality of life, and a few have paired it with black cohosh. This is a separate, more limited area of research than the core depression evidence and is not established by the references cited here.

Supported by Trial 1

Mechanism of action

1

Multi-neurotransmitter reuptake inhibition

Hyperforin inhibits neuronal reuptake of serotonin, dopamine, norepinephrine, GABA, and glutamate simultaneously by activating sodium conductive transient receptor potential channel 6 (TRPC6) — a unique mechanism entirely different from SSRIs or SNRIs. This broad neurotransmitter modulation explains both the antidepressant efficacy and the mild anxiolytic effects.

2

HPA axis and cortisol normalization

SJW normalizes HPA axis hyperactivity in depression by reducing CRH and ACTH-stimulated cortisol hypersecretion — addressing a key biological abnormality in major depression. Hypericin specifically appears to modulate glucocorticoid receptor sensitivity, restoring normal cortisol feedback regulation.

3

CYP3A4 and P-glycoprotein induction

Hyperforin strongly induces CYP3A4, CYP2C9, and intestinal P-glycoprotein expression via pregnane X receptor (PXR) activation — dramatically increasing the metabolism and elimination of numerous medications. This mechanism underlies the most clinically significant herb-drug interactions in herbal medicine.

Clinical trials

1
St. John's Wort vs. Antidepressants — Meta-Analysis of 29 RCTs
PubMed

Comprehensive meta-analysis of 29 RCTs (5,489 patients) comparing SJW to placebo and standard antidepressants for mild-to-moderate depression.

5,489 patients with mild to moderate depression across 29 RCTs.

SJW significantly more effective than placebo (RR 1.48). Comparable efficacy to standard antidepressants (RR 1.01). Significantly fewer patients dropped out due to adverse effects vs. antidepressants (0.8% vs. 3.0%). Established SJW as evidence-based treatment for mild-to-moderate depression.

2
St. John's Wort and Seasonal Affective Disorder — RCT
PubMed

Randomized, double-blind trial of SJW extract vs. light therapy vs. combination in 301 patients with seasonal affective disorder.

301 SAD patients. Winter season intervention.

SJW monotherapy equally effective to bright light therapy for SAD. Combination of SJW + light therapy showed trend toward greater improvement. Both treatments well-tolerated. Establishes SJW as effective SAD treatment.

Side effects and drug interactions

Common Potential side effects

Photosensitivity — increased sensitivity to UV radiation; wear sunscreen, especially fair-skinned individuals at higher doses
GI upset, dry mouth, dizziness, fatigue in small percentage
Sexual dysfunction (reduced libido) at rates lower than SSRIs but still reported
Do not use for severe depression — evidence limited to mild-to-moderate; seek professional care for severe depression

Important Drug interactions

Critical — major drug interactions: SJW induces CYP3A4, CYP2C9, and P-glycoprotein, reducing blood levels of many medications:
Oral contraceptives — SJW can cause contraceptive failure leading to unintended pregnancy; avoid combination
HIV antiretrovirals (indinavir, nevirapine) — SJW markedly reduces drug levels; can lead to treatment failure
Cyclosporine (transplant rejection drug) — SJW reduces levels to sub-therapeutic; has caused transplant rejection
Warfarin — significantly reduced anticoagulation; INR drops; increased clotting risk
Digoxin — reduced levels; risk of cardiac decompensation
Antidepressants and other serotonergic drugs (SSRIs, SNRIs, triptans, MAOIs) — risk of serotonin syndrome; never combine with MAOIs, and do not add to or replace a prescribed antidepressant without medical supervision

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Frequently asked questions about St. John's Wort (Hypericum perforatum)

What is St. John's wort used for?

St. John's wort is one of the most studied botanicals for supporting mood and emotional wellbeing, particularly mild low mood. It is thought to influence serotonin and other neurotransmitters.

How much St. John's wort should I take?

Studies commonly use extracts standardized to 0.3% hypericin (or to hyperforin) at about 300 mg three times daily, for 900 mg total. Standardization matters, so check the label.

What medications interact with St. John's wort?

This is critical: St. John's wort speeds up the breakdown of many drugs, reducing their effectiveness. It interacts with antidepressants, birth control pills, blood thinners, and some heart and HIV medications, among others. Never combine it with prescription drugs without your doctor's guidance.

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

Mood benefits typically build over 4 to 6 weeks of consistent use. Because of its many serious drug interactions and the importance of proper mood care, talk to a healthcare provider before starting it.

What is St. John's Wort?

St. John's Wort is a flowering plant with over 2,000 years of medicinal use and one of the most extensively studied herbal antidepressants. Its active compounds hypericin and hyperforin have demonstrated antidepressant effects comparable to standard pharmaceutical antidepressants in multiple meta-analyses — with a sign…

What is the recommended dosage of St. John's Wort?

The clinically studied dose is 300 mg three times daily (900 mg/day) standardized to 0.3% hypericin; some extracts standardized to 3–5% hyperforin; 4–6 weeks for full antidepressant effect Always follow the product label and check with a healthcare provider for personal advice.

Is St. John's Wort safe, and does it have side effects?

For most healthy adults, St. John's Wort is well tolerated at studied doses. Reported effects can include: Photosensitivity — increased sensitivity to UV radiation; wear sunscreen, especially fair-skinned individuals at higher doses GI upset, dry mouth, dizziness, fatigue in small percentage It may also interact with some medications. St. John's Wort is not right for everyone, so check with a healthcare provider first if you are pregnant or breastfeeding, have a medical condition, or take prescription medication.

Does St. John's Wort interact with any medications?

Possible interactions include: Critical — major drug interactions: SJW induces CYP3A4, CYP2C9, and P-glycoprotein, reducing blood levels of many medications: Oral contraceptives — SJW can cause contraceptive failure leading to unintended pregnancy; avoid combination If you take prescription medication, check with a pharmacist or doctor before using it.

How strong is the scientific evidence for St. John's Wort?

NutraSmarts rates the evidence for St. John's Wort as Strong (4 out of 5). It is backed by 2 clinical trials and 5 cited references summarized on this page. A higher rating reflects more, larger, and better-designed human studies.

References(5 citations)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

  1. Linde K, Berner MM, Kriston L. St John's wort for major depression. Cochrane Database Syst Rev. 2008;2008(4):CD000448. doi: 10.1002/14651858.CD000448.pub3.PubMedUsed to support: Primary positive evidence for the mild-to-moderate depression claim: this Cochrane review of 29 trials (5489 patients, mostly mild-to-moderate symptoms) found hypericum extracts superior to placebo and similarly effective to standard antidepressants with fewer side effects. Notably, the authors caution that trials from German-speaking countries reported more favorable results and that benefit in more severely depressed/major-depression populations is less certain.
  2. Hypericum Depression Trial Study Group; Davidson JR, Gadde KM, Fairbank JA, Krishnan KR, Califf RM, et al. Effect of Hypericum perforatum (St John's wort) in major depressive disorder: a randomized controlled trial. JAMA. 2002;287(14):1807-14. doi: 10.1001/jama.287.14.1807.PubMedUsed to support: The pivotal negative trial, stated plainly: this large NIH/NCCAM-funded, double-blind RCT (340 outpatients with major depression, with a sertraline arm) found St John's wort was NO better than placebo for moderately severe major depression on the primary outcomes. St John's wort does not work for major (more severe) depression.
  3. Borrelli F, Izzo AA. Herb-drug interactions with St John's wort (Hypericum perforatum): an update on clinical observations. AAPS J. 2009;11(4):710-27. doi: 10.1208/s12248-009-9146-8.PubMedUsed to support: Required safety/interaction reference: documents that St John's wort induces CYP3A4 and P-glycoprotein, lowering plasma levels and efficacy of many drugs including oral contraceptives, warfarin, cyclosporine/tacrolimus (immunosuppressants), indinavir and other antiretrovirals, digoxin and statins, and can cause serotonin syndrome with serotonergic drugs. These interactions can be clinically serious.
  4. Apaydin EA, Maher AR, Shanman R, Booth MS, Miles JN, Sorbero ME, et al. A systematic review of St. John's wort for major depressive disorder. Syst Rev. 2016;5(1):148. doi: 10.1186/s13643-016-0325-2.PubMedUsed to support: Independent (RAND) systematic review of 35 studies that contextualizes the mood claim: St John's wort showed greater response than placebo and comparable efficacy to antidepressants with fewer adverse events in major depressive disorder, but the authors stress that most trials were short, of mild-to-moderate severity, heterogeneous in extract/dose, and that drug-interaction risk limits clinical use.
  5. Wheatley D Hypericum in seasonal affective disorder (SAD) Current Medical Research and Opinion. 1999;Curr Med Res Opin. 1999;15(1):33-37.PubMedUsed to support: Small older trial of St John's Wort in seasonal affective disorder (SAD), with SJW alone and combined with light therapy. Supports the SAD use as a separate, limited-evidence application; SAD is a form of depression and requires clinician evaluation.