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St. John's Wort

St. John's Wort

Best for

Ease depression symptoms

Proven modest benefit 810 mg/day 12 weeks 2 meta-analyses, n=8.1k #1 of 36 studied

St. John’s wort provides a proven modest benefit for depressive symptoms, while evidence across other outcomes remains too limited to outweigh important medication-interaction concerns.

Median effective dose, most-studied outcomes

Full protocol, 3 outcomes

Risk, worst reported severity

  • drowsiness mild
  • gastrointestinal upset, headache, sleep disturbance, dizziness mild
  • warfarin major
  • cyclosporine major
All 18 events and interactions

What st. john's wort actually does

Outcome Effect Evidence Dose Time Rank
Modest benefits 1
Ease depression symptoms Proven modest benefit Depression can bring persistent low mood and loss of interest in daily life.
small 		2 meta-analyses 3 papers · n=8.1k 810 mg 12 wk #1 /36
Early research 2
Better quality of life Not enough research Health can shape daily life, well-being, and a person's sense of control.
trivial 		1 RCT 1 papers · n=81 810 mg 12 wk —
Improve your social life Not enough research Social functioning reflects how well relationships and everyday social roles are going.
trivial 		1 RCT 1 papers · n=25 810 mg 12 wk —

Effect tiers come from native-unit MCID where available, Cohen's d otherwise.

Protocol

Dose, timing & forms

How much

For depressive symptom severity, the clearest studied protocol is 810 mg daily for 12 weeks. The reviewed evidence shows a small benefit, so do not expect a quick or dramatic shift in how you feel.1 The same daily amount appeared in the limited quality-of-life and social-function research, but those outcomes remain too uncertain to guide a reason for use.1

When and how long

The trial evidence supports taking St. John's wort consistently every day across a multi-week course, not using it only when mood dips.1 The available protocols do not establish a best time of day, meal pairing, or split schedule, so follow the product directions unless a clinician or pharmacist gives you a different plan. Check interactions before the first dose, since the drug-processing effect is the central timing issue here.2

Forms & standardisation

Look for an oral extract with a clearly named botanical species, Hypericum perforatum, and a stated amount per daily serving. The evidence does not show that every tea, powder, or extract works interchangeably, so avoid treating a label's “St. John's wort” claim as proof that it matches the extracts used in trials.1 Standardization details can help identify a consistent product, but they do not remove the interaction risk driven largely by hyperforin.2

Studied range, by outcome

Outcome Studied range Median effective Duration Evidence
Reduce overall depressive symptom severity 810 mg — 12 wk 3 papers
Support better everyday quality of life 810 mg — 12 wk 1 paper
Take part more fully in social life 810 mg — 12 wk 1 paper

Adverse events and drug interactions

Safety events

drowsiness mild
gastrointestinal upset, headache, sleep disturbance, dizziness mild
headache mild
allodynia mild
erythrodermia mild
hypophosphatemia mild
paresthesia mild
nausea mild

Drug interactions

warfarin major decreases concentration
warfarin major decreases effect
cyclosporine major decreases concentration
ethinyl estradiol major decreases concentration
norethindrone major decreases concentration
indinavir major decreases concentration
ritonavir major decreases concentration
nevirapine major decreases concentration
methadone major decreases concentration
imatinib major decreases concentration
In context

What this is and how it works

  • Across 3 studies (n=8,091), St. John’s wort improved depression symptoms; a pooled effect size and MCID comparison were not reported.1
  • Six papers reviewed here span 13 outcomes, with strongest evidence concentrated on depressive symptoms.
  • St. John’s wort can increase prescription-drug metabolism, including medicines affected by pregnane X receptor activation.2

St. John's wort is a yellow-flowering plant, Hypericum perforatum, sold as capsules, tablets, teas, and extracts. Its modern use centers on mood, but the extract contains many active plant compounds rather than one single ingredient.1

In the brain, St. John's wort compounds appear to influence the chemical messages that nerve cells use to communicate, which gives researchers a plausible explanation for its small mood signal in trials.1 Its bigger practical trick happens in the liver: hyperforin flips on a drug-processing switch, like opening extra checkout lanes that move some medicines out of the body faster.2

Bottom line

St. John's wort suits someone considering a carefully monitored, 12-week trial for depressive symptoms who takes no interacting medicines and accepts that the expected benefit is small.1 Skip self-starting it if you use warfarin, cyclosporine, or hormonal contraceptive ingredients, and ask a pharmacist or clinician to review your full medication list first.2 The early findings on quality of life and social functioning are not strong enough to drive the decision.1

Frequently asked

Common questions

Does St. John's wort work for depression symptoms?

The reviewed trials show a small improvement in depressive symptom severity after 12 weeks. That is a real signal, but it is not a dramatic change, and the herb's interaction risk matters just as much as its possible benefit.1

Why does St. John's wort interact with so many medicines?

St. John's wort activates a liver control switch that speeds up the processing of many medicines. That can lower medicine levels enough to reduce their intended effect, including with warfarin, cyclosporine, and some oral contraceptive ingredients.2

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

The main depressive-symptom trials assessed results at 12 weeks, so judge it as a daily, multi-week trial rather than something for an occasional bad day.1

Sources

Sources

  1. 1. St John's wort for major depression (2008) ↑
  2. 2. St. John's wort induces hepatic drug metabolism through activation of the pregnane X receptor (2000)

Generated August 27, 2026

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