St. John's Wort and SSRI: interaction risk (contraindicated)
Severity contraindicated. St. John's Wort with an SSRI risks serotonin syndrome — do not combine. Worth a pharmacist conversation before combining. Interaction-evidence certainty: high.
Severity: contraindicated
- contraindicatedSt. John's Wort + SSRI: St. John's Wort with an SSRI risks serotonin syndrome — do not combine.
How serious is this?
Severity contraindicated means: documented risk of clinically important adverse effects when St. John's Wort is combined with SSRI. Combining is not recommended without prescriber oversight. The evidence base itself is high — interaction records are usually built from case reports and pharmacokinetic reasoning, not RCTs, and we say so plainly.
Mechanism
Interaction type: additive-risk. Mechanism-specific detail is thin in the source data — treat as a signal to consult a pharmacist rather than a fully-characterised interaction.
Does this apply to other selective serotonin reuptake inhibitor drugs?
No other selective serotonin reuptake inhibitor drugs modeled yet. When mechanism is receptor- or enzyme-based, treat class members as probably-similar until data proves otherwise.
Spacing & timing
No studied separation window for this interaction. Absence of data is not absence of risk — if the mechanism is pharmacodynamic (additive sedation, receptor-level effects), spacing does not fix it.
Grade history
No grade changes yet. Initial grade assigned; re-reviewed on every 6 months (moderate+ severity) — next review by . Methodology v1.
Re-review cadence: every 6 months (moderate+ severity) · next scheduled by · methodology v1.
Frequently asked
Can I take St. John's Wort and SSRI together?
Severity is the shorthand; the mechanism and studied evidence matter. Read the severity block and the mechanism block — combined they answer this in a way a single yes/no can't.
What if I already took St. John's Wort with SSRI?
If symptoms appeared, contact your pharmacist or Poison Control. If nothing happened and severity is low, note it and avoid habitual co-use without a pharmacist's OK.
How far apart should I space St. John's Wort and SSRI?
Only meaningful when the interaction is chelation- or absorption-based and studied. If the mechanism is pharmacodynamic (additive sedation, serotonergic load), spacing does not fix it.
Does the St. John's Wort + SSRI interaction apply to other drugs in the same class?
Interactions are usually class-wide when the mechanism is at the receptor/enzyme, not the specific molecule. The mechanism block above tells you which case this is.
Should I tell my doctor I take St. John's Wort?
Yes — pharmacists especially. The single most useful thing you can do about supplement interactions is put them on your medication list.
Related
Not medical advice. Absence of a recorded interaction is not a guarantee — check with your prescriber.
Cite this page
Reuse under CC-BY 4.0 with attribution to evidencebased.info.
Plain-text citation
Substrate. St. John's Wort and SSRI: interaction risk (contraindicated). https://evidencebased.info/interactions/st-johns-wort-and-ssri. Updated 2026-07-14.
BibTeX
@misc{substrate_nsstjohnswortandssri,
author = {Substrate editorial},
title = {St. John's Wort and SSRI: interaction risk (contraindicated)},
year = {2026},
url = {https://evidencebased.info/interactions/st-johns-wort-and-ssri},
note = {evidencebased.info}
}