St. John’s Wort Side Effects: Risks, Precautions, and Drug Interactions
Essential safety insights and interaction alerts for anyone considering herbal remedies.
St. John’s Wort (Hypericum perforatum) has been used for centuries as an herbal remedy, most notably for mild and moderate depression. Despite its natural origin, St. John’s Wort is associated with significant side effects, precautions, and a high potential for drug interactions. This article comprehensively examines the adverse effects, safety concerns, and key warnings associated with St. John’s Wort use, helping you make informed decisions about this widely-available supplement.
What Is St. John’s Wort?
St. John’s Wort is a flowering plant native to Europe but now found worldwide. Its extracts are widely available as teas, capsules, tablets, and topical products. Traditionally, it has been most commonly used for the treatment of mild to moderate depression and anxiety. Modern research continues to investigate its efficacy, but concern about its safety centers on its interaction with numerous medications and possible side effects.
Common Side Effects of St. John’s Wort
In general, St. John’s Wort is considered safe for most adults when taken orally at recommended doses (up to 900 mg daily for 12 weeks). Adverse effects occur more often at higher doses or with long-term use. The most commonly reported side effects include:
- Digestive Issues: Diarrhea, constipation, upset stomach, nausea, dry mouth
- Nervous System Effects: Dizziness, headache, anxiety, restlessness, trouble sleeping (insomnia), tiredness
- Skin and Sensory Reactions: Increased sensitivity to sunlight (photosensitivity), skin tingling or irritation
- Allergic Reactions: Rash, itching, or swelling, especially in people sensitive to the plant
Serious skin reactions may occur after exposure to sunlight (even normal amounts), resulting in sunburn or rash (photosensitivity). Fair-skinned individuals and those exposed to strong sunlight are at particular risk. Sunscreen and protective clothing are recommended while using the supplement.
Rare and Serious Side Effects
While less common, some users have experienced more serious adverse effects. These can include:
- Worsening psychotic symptoms in people with schizophrenia
- Mania induction and rapid mood cycling in people with bipolar disorder
- Hypertensive crisis (sudden, severe increase in blood pressure), especially if combined with certain foods or medications
- Liver, renal, and reproductive system disturbances (in rare instances)
- Serotonin syndrome when combined with other serotonergic drugs (see interactions below)
- Severe sedation (when combined with specific antidepressants such as paroxetine)
Precautions and Safety Warnings
Despite being available over-the-counter in many countries, St. John’s Wort should be used with caution and under medical supervision. Special warnings apply for certain populations and health conditions:
Pregnancy and Breastfeeding
- Pregnancy: St. John’s Wort is possibly unsafe when taken orally during pregnancy and may cause birth defects. No sufficient data supports its safety, so it should be avoided during pregnancy.
- Breastfeeding: The supplement can be passed to infants through breast milk, potentially causing colic, drowsiness, and fussiness in children. Avoid use while breastfeeding unless specifically directed by a healthcare provider.
Children and Adolescents
- St. John’s Wort appears possibly safe for use by children aged 6–17 for up to 8 weeks at typical doses. Its use in children should always be monitored by a medical professional.
Mental Health Disorders
- Schizophrenia: May provoke psychosis or worsening of symptoms.
- Bipolar Disorder: Risk of triggering mania or rapid cycling between depressive and manic phases.
- Major Depression: Possible risk of mania, impulsivity, or severe agitation, particularly if combined with other antidepressants.
- Alzheimer’s Disease: May worsen dementia symptoms.
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Surgical Considerations
- St. John’s Wort can affect brain serotonin levels and interfere with anesthesia and other medications used during surgery. It is recommended to discontinue use at least two weeks before any planned surgery.
Drug Interactions: Medications to Avoid
St. John’s Wort is particularly problematic due to its high potential to interact with prescription and over-the-counter medications. It induces enzymes in the liver (notably CYP3A4), causing the body to metabolize certain drugs more quickly, reducing their effectiveness or, in some cases, causing dangerous side effects. Key interactions include:
| Drug/Drug Class | Interaction Outcome |
|---|---|
| Antidepressants/SSRIs (e.g., paroxetine, fluoxetine) | Increased risk of serotonin syndrome (agitation, confusion, rapid heart rate, high blood pressure, fever, seizures) |
| Birth Control Pills | Reduced effectiveness and potential for unintended pregnancy |
| Blood Thinners (warfarin) | Decreased anticoagulant effect, increasing risk of blood clots |
| Immunosuppressants (cyclosporine, tacrolimus) | Reduced levels, higher rejection risk for transplant patients |
| HIV Medications (protease inhibitors, NNRTIs) | Reduced antiviral effect and risk of treatment failure |
| Cancer Medications (irinotecan, imatinib) | Decreased efficacy of chemotherapy agents |
| Anti-seizure medications | Possible reduced effectiveness, higher risk of breakthrough seizures |
| Statins (cholesterol-lowering drugs) | Reduced effectiveness, raising cholesterol risk |
| Triptans (migraine medications) | Risk of serotonin syndrome |
| Clozapine (antipsychotic) | Decreased blood level, reduced effectiveness |
| Some antifungals (voriconazole) | Reduced blood level, decreased anti-fungal activity |
| Digoxin, Oxycodone, Other CYP3A4 Metabolized Drugs | Reduced levels, lower effectiveness |
Key Points About Drug Interactions
- If you are taking prescription medication, consult your healthcare provider before starting St. John’s Wort.
- Many negative interactions may not have noticeable symptoms but can significantly reduce the effectiveness of critical medications.
- High-risk groups include individuals on medication for depression, anxiety, migraine, seizures, HIV, cancer, and organ transplants.
When Should You Avoid St. John’s Wort?
Avoid use of St. John’s Wort entirely (unless specifically recommended by your physician) if you:
- Are pregnant or breastfeeding
- Take prescription drugs, especially those listed in the interaction table above
- Have a history of bipolar disorder, schizophrenia, or certain other psychiatric disorders
- Are scheduled for surgery
- Have sensitivity to sunlight or take other drugs that increase sun sensitivity
Always inform your healthcare provider about any supplements you take, including herbal remedies like St. John’s Wort.
Things to Remember Before Using St. John’s Wort
- Start with a low dose and use only for short durations unless otherwise directed by a professional.
- Monitor yourself for signs of hypersensitivity, skin reactions, unexpected mood changes, or interactions with other medications.
- Store away from sunlight, heat, and moisture to preserve potency and prevent degradation.
Do not stop prescribed antidepressant, anticonvulsant, cancer, HIV, or immunosuppressant medications in favor of (or in conjunction with) St. John’s Wort without medical approval.
Possible Alternatives to St. John’s Wort
If seeking alternatives for mild depression or anxiety, consider:
- Regular physical activity
- Cognitive behavioral therapy (CBT)
- Other evidence-based therapies or prescribed medications
- Mindfulness and stress-reduction practices
Always discuss alternative approaches with your healthcare provider. Self-medicating—especially with potent herbal supplements—is not recommended when options can be tailored safely for your needs.
Frequently Asked Questions (FAQs)
What are the signs of an allergic reaction to St. John’s Wort?
Symptoms may include rash, hives, swelling, severe dizziness, and trouble breathing. Seek medical attention immediately if these occur after use.
Can St. John’s Wort be used long term?
Most studies suggest use is generally safe for up to 12 weeks. Longer-term safety data is insufficient; use beyond this period should only be considered under medical supervision.
Is it safe to combine St. John’s Wort with antidepressant medications?
No. Combining St. John’s Wort and other antidepressants (like SSRIs) can trigger a dangerous reaction called serotonin syndrome. This may involve confusion, rapid heart rate, high blood pressure, fever, and seizures.
Does St. John’s Wort reduce the effectiveness of birth control?
Yes. St. John’s Wort can lower blood levels of estrogen and progesterone in contraceptives, substantially increasing the risk of unintended pregnancy.
Is topical use of St. John’s Wort safe?
Limited research exists on topical safety. Skin reactions, especially upon light exposure, have been reported. Only use topical products at low concentration and avoid sun exposure.
Who should not take St. John’s Wort?
Pregnant and breastfeeding women, children unless prescribed, those with psychiatric conditions (bipolar disorder, schizophrenia), those expecting surgery, and anyone taking interacting medications should avoid St. John’s Wort.
Conclusion: Should You Use St. John’s Wort?
St. John’s Wort may offer relief for mild depression, but its potential for drug-drug interactions and adverse effects is high. Individuals using the supplement should do so cautiously, under professional supervision, and never in combination with interacting prescriptions or in place of established medical therapies. Natural does not always mean safe—stay informed and protect your health.
References
- https://www.webmd.com/vitamins/ai/ingredientmono-329/st-johns-wort
- https://www.mayoclinic.org/drugs-supplements-st-johns-wort/art-20362212
- https://pmc.ncbi.nlm.nih.gov/articles/PMC9587902/
- https://www.nccih.nih.gov/health/st-johns-wort
- https://www.merckmanuals.com/professional/special-subjects/dietary-supplements/st-john-s-wort
- https://www.mind.org.uk/information-support/drugs-and-treatments/complementary-and-alternative-therapies/st-johns-wort/
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