mental

St. John's Wort

St. John's wort is a plant with yellow flowers that has been widely used in traditional medicine. It may be helpful for mild or moderate depression, but it's uncertain whether this holds for severe depression or for longer than 12 weeks. For other conditions, the evidence is insufficient to allow definite conclusions.

St. John's wort is a plant with yellow flowers that has been widely used in various systems of traditional medicine. It has also been used widely as an herbal treatment for depression.

Research & evidence

Strong support Some support Weak or no supportColours show how well the sources back each point. The reason is next to each one.

St. John's wort may be helpful for mild or moderate depression. NCCIH says it appears to be more effective than a placebo and as effective as standard antidepressant medications for mild or moderate depression. It's uncertain whether this is true for severe depression or for time periods longer than 12 weeks.

Moderate evidenceSome support. Shown only in certain groups, uses, strains or doses

Study details

NCCIH: "it may be helpful for mild or moderate depression" "appears to be more effective than a placebo" "as effective as standard antidepressant medications for mild or moderate depression." "It's uncertain whether this is true for severe depression or for time periods longer than 12 weeks."

Source: NCCIH, St. John's Wort (Last Updated May 2025), How Much Do We Know? View source

For conditions other than mild or moderate depression, the evidence is insufficient to allow definite conclusions about the usefulness of St. John's wort.

Limited evidenceSome support. Not enough good evidence to say

Study details

NCCIH: "For other conditions, the evidence is insufficient to allow definite conclusions"

Source: NCCIH, St. John's Wort (Last Updated May 2025), How Much Do We Know? View source

Dosage

Form	Amount
Any form	No standard dose is listed by our sources.

Dosage varies by body weight, age, sex, existing health conditions, current medications, and pregnancy/breastfeeding status. The amounts above reflect commonly studied or commonly recommended amounts, not a personal prescription. Always consult a healthcare provider before starting a new supplement, especially if you are pregnant, breastfeeding, managing a chronic condition, or taking medication.

Side effects

Side effects can include diarrhea, dizziness, trouble sleeping, restlessness and skin tingling. It might cause severe skin reactions after sun exposure. It can weaken the effects of many medicines, including crucially important medicines.

Well documented Reported (case reports, anecdotal or one study) None reportedThe circle shows how well documented an effect is, not how serious it is. A rarely reported effect can still be serious, so always read ‘When to stop’.

Effect	Frequency	When to stop
Diarrhea, dizziness, trouble sleeping, restlessness, skin tinglingWell documentedListed plainly by NIH, MSK or LiverTox	Not stated	Stop and talk to a doctor if it persists.
Severe skin reactions after sun exposure, if taken by mouth in large doses or applied to the skinWell documentedListed plainly by NIH, MSK or LiverTox	Not stated	Avoid strong sun while using it; stop and see a doctor if you get a skin reaction.

Safety & interactions

Safety

For most adults who are not taking any kind of medicine, St. John's wort appears to be safe when used for up to 12 weeks, and some studies indicate it can be used safely for a year or more. NCCIH says it has been clearly shown that St. John's wort can interact in dangerous, sometimes life-threatening ways with a variety of medicines, and that interactions can weaken the effects of life-saving medicines or cause dangerous side effects (see Drug interactions). LiverTox says that in controlled trials it has not been linked to serum enzyme elevations or to clinically apparent liver injury.

Contraindications

It may be unsafe to use St. John's wort during pregnancy because it may increase the risk of birth defects. Breastfeeding infants of mothers who take St. John's wort can experience colic, drowsiness and lethargy. St. John's wort can weaken the effects of many medicines, including crucially important ones (see Drug interactions). If you take any type of medicine, talk with your health care provider before using it.

Drug interactions

Many medicinesEstablished

NCCIH says it has been clearly shown that St. John's wort can interact in dangerous, sometimes life-threatening ways with a variety of medicines. It can weaken the effects of many medicines, including crucially important ones such as some antidepressants (amitriptyline, bupropion), birth control pills, cyclosporine (which prevents the body from rejecting transplanted organs), some seizure drugs (phenytoin, carbamazepine), some heart medicines (digoxin, ivabradine), some HIV drugs (indinavir, nevirapine), some cancer medicines (irinotecan, imatinib, docetaxel), warfarin and certain statins (simvastatin). LiverTox advises caution, and checking for specific interactions, with any other medication.

Birth control pillsEstablished

LiverTox says St. John's wort has major drug interactions, particularly with birth control pills.

Transplant rejection (anti-rejection) medicines, including cyclosporine and tacrolimusEstablished

LiverTox says St. John's wort has major drug interactions, particularly with transplant rejection agents, and that it can lower concentrations of cyclosporine and tacrolimus.

Antiretroviral (HIV) medicines, including indinavir, nevirapine and HIV protease inhibitorsEstablished

LiverTox says St. John's wort has major drug interactions, particularly with antiretroviral agents, and names HIV protease inhibitors and indinavir among the drugs affected.

Heart medicines, including digoxin and ivabradineEstablished

LiverTox says St. John's wort has major drug interactions, particularly with digoxin, and that it can lower concentrations of digoxin.

Blood thinners (anticoagulants and platelet inhibitors), including warfarin and aspirinEstablished

LiverTox says St. John's wort has major drug interactions, particularly with platelet inhibitors and anticoagulants, and names warfarin and aspirin among the drugs affected.

Psychotropic medicines, including SSRIsEstablished

LiverTox says St. John's wort has major drug interactions, particularly with psychotropic agents, and lists case reports of serotonin syndrome with SSRIs. NCCIH warns of possible increased serotonin-related side effects, which can be serious.

Drugs affected by CYP3A4 and related enzymes or by P-glycoprotein (e.g., fexofenadine, methadone, midazolam, simvastatin, theophylline)Documented

LiverTox says in vivo studies show St. John's wort induces CYP3A4, 1A and 2C9 as well as P-glycoprotein, leading to a lowering of serum levels of many drugs, such as amitriptyline, cyclosporine, digoxin, fexofenadine, indinavir, methadone, midazolam, simvastatin, tacrolimus, theophylline and warfarin.

Acetaminophen and other medicines that can affect the liverTheoretical

LiverTox says St. John's wort can potentiate the intrinsic hepatotoxicity of other agents such as acetaminophen, and may increase or decrease the likelihood of drug induced liver injury from other medications.

Seizure medicines (e.g., phenytoin, carbamazepine)Established

NCCIH says St. John's wort can weaken the effects of some drugs used to prevent seizures, including phenytoin and carbamazepine.

Cancer medicines (e.g., irinotecan, imatinib, docetaxel)Established

NCCIH says St. John's wort can weaken the effects of some cancer medications, including irinotecan, imatinib and docetaxel.

Statins (e.g., simvastatin)Established

NCCIH says St. John's wort can weaken the effects of certain statins, including simvastatin; LiverTox lists simvastatin among drugs whose blood levels it lowers.

Established: stated plainly by an authoritative source. Documented: supported by case reports or trial data. Theoretical: based on mechanism, animal data, or a cautious listing. Always check with your pharmacist or prescriber.