St. John's Wort: Everything You Need to Know

St. John’s wort is a wildflower found in Europe and Asia that blossoms in June, near the time of the feast of St. John the Baptist.

St. John’s wort contains at least 10 types of bioactive compounds known to have antioxidant, antidepressant, antibacterial, and anti-inflammatory activity.

Historically touted for its effectiveness in wound care, infections, and mental health, it's now most commonly used for depression.

This article discusses the latest evidence about St. John’s wort's benefits and safety information to remember if you decide to add it to your medicine cabinet.

Uses of St. John's Wort

Extracts of St. John’s wort are most commonly used for depression. Clinical trials have also studied it for skin conditions and menopause symptoms. the following is information on its effectiveness.

Depression

Depression is the most common mental illness, affecting close to 4% of people worldwide. It is characterized by symptoms like sadness, anxiety, decreased appetite, and anhedonia (the loss of pleasure in activities).

St. John’s wort is prescribed for depression in some European countries and is commonly used as an OTC supplement in the United States.

Studies show that around 56% of people who use St. John’s wort respond positively to treatment vs. 35% of people treated with a placebo (sugar pill without active medicine).

St. John’s wort is as effective as a common class of prescription antidepressants called selective serotonin reuptake inhibitors (SSRIs) for mild to moderate depression.

It's mainly been studied short-term for up to twelve weeks. This means that long-term effects are uncertain. And it's unclear if St. John’s wort benefits severe depression or suicidality.

Skin Disorders

St. John’s wort has a long history of use for various skin conditions, such as the following:

• Wounds
• Burns
• Sunburns
• Bruises

The component hyperforin in the herb is believed to be responsible for St. John’s wort's antibacterial effects and wound care benefits.

Clinical trials are rare, however. It has been researched in small human trials for the following:

• Acne
• Atopic dermatitis
• Psoriasis

Though it may benefit these conditions, larger trials are needed before it can be recommended for routine use.

Menopausal Symptoms

A study of 80 postmenopausal females showed that those who took St. John’s wort for two months had fewer menopausal symptoms, including hot flashes and depression, than those who didn't.

Despite this, a review concluded that there isn't enough evidence that St. John’s wort is safe and effective for menopause.

Additional Uses

St. John’s wort has also been studied for the following conditions, but more data is needed before it can be recommended:

• Pain management
• Dental hygiene after surgery
• Premenstrual syndrome (PMS)
• Premenstrual dysphoric disorder
• Obsessive-compulsive disorder (OCD)

What Are the Side Effects of St. John's Wort?

Your provider may recommend you take St. John’s wort for depression or another condition.

However, supplements like St. John’s wort may have potential side effects.

These side effects may be common and mild or rare and severe. 

Common Side Effects

Research suggests that most side effects of St. John’s wort are mild and relatively rare, particularly compared to those of prescription antidepressants.

Side effects typically occur in less than 3% of people who use St. John’s wort and can include the following:

• Stomach upset
• Fatigue
• Restlessness
• Allergic reactions
• Dizziness
• Confusion
• Dry mouth

Severe Side Effects

St. John’s wort has been reported to cause the following severe side effects:

• Hypertensive crisis
• Mania
• Kidney toxicity
• Sun sensitivity, particularly at high doses, such as 2 to 4 grams (g) a day
• Cardiovascular collapse

If taken with other medicines that increase serotonin levels, such as antidepressants and some migraine medicines, St. John’s wort can contribute to serotonin syndrome. This can be life-threatening.

Symptoms of serotonin syndrome include the following:

• Tachycardia (increased heart rate)
• Hypertension (Increased blood pressure)
• Sweating
• Hallucinations

Should you experience any of these, seek medical help immediately.

Precautions

Do keep the following precautions in mind when using St. John’s wort:

• Severe allergic reaction: Avoid using St. John’s wort if you have a known allergy to it or its ingredients. Ask your pharmacist or healthcare provider for a complete list of the ingredients if you need clarification.
• Pregnancy: Although St. John’s wort has been used safely in clinical trials of pregnant women, it is not typically recommended during pregnancy. This is because it's not been proven effective and has caused congenital disabilities in animal models.
• Breastfeeding: St. John’s wort is not recommended during breastfeeding. It may be passed through breast milk to the infant and cause colic, sleepiness, or fussiness.
• Adults over age 65: Interactions between St. John’s wort and prescription medications may be more likely in this population. Discuss your medications, including prescriptions, OTC products, and supplements, with a healthcare provider or pharmacist before adding St. John’s wort.
• Children: There's not enough safety data to recommend St. John’s wort for children.

Dosage: How Much St. John's Wort Should I Take?

For depression, the typical dose of St. John’s wort is 300 milligrams (mg) three times a day.

What Happens If I Take Too Much St. John's Wort?

There is little available data on St. John’s wort toxicity. One older (2009) trial concluded that daily doses of 500 mg were safe for up to one year, but more, long-term studies are needed.

The typical daily dose for depression (900 mg) is almost twice that used in the trial.

High doses of St. John’s wort, between 2 and 4 grams daily, are more likely to cause side effects like sun sensitivity.

Interactions

St. John’s wort is perhaps the biggest herbal "offender" in terms of drug interactions. It is known to interact with myriad prescription medicines. For instance, if it's taken with other antidepressants, St. John’s wort increases the risk of serotonin syndrome, a life-threatening condition characterized by a racing heart rate, high blood pressure, and hallucinations.

St. John’s wort induces (increases the activity of) an enzyme called cytochrome P450 3A4. This enzyme metabolizes (breaks down) lots of medicines in the body. If these medicines are taken with St. John’s wort, they are broken down faster and will be less effective.

St. John’s wort lowers the effectiveness of the following medicines:

• Antidepressants
• Birth control pills
• Seizure medications like carbamazepine and phenytoin
• Blood pressure medications like amlodipine and losartan
• Pain medications like oxycodone
• Medications to prevent organ transplant rejection, such as cyclosporine and tacrolimus
• Heart medications like digoxin
• Human immunodeficiency virus (HIV) drugs
• Cancer medications
• Blood thinners like Jantoven (warfarin) and Plavix (clopidogrel)
• Cholesterol-lowering medicines, including Zocor (simvastatin)

Hyperforin is believed to cause the herb's numerous drug interactions. In theory, taking less than 1 mg of hyperforin daily is unlikely to cause interactions. However, supplements aren't regulated in the same way drugs are in the United States, and researchers have found hyperforin levels can vary greatly between products.

It is essential to carefully read a supplement's ingredients list and nutrition facts panel to know which ingredients and how much of each ingredient is included. Please review the supplement label with your healthcare provider to discuss potential interactions with foods, other supplements, and medications.

How to Store St. John's Wort

Store St. John’s wort in a cool place, away from children and pets. It should be kept away from direct light.

Discard after one year or according to the manufacturer's directions.

Similar Supplements

Some other herbs that have been studied in human trials for depression include the following:

• Saffron
• Curcumin
• English lavender
• Rhodiola

Other supplements that may be helpful for depression include the following:

• S-adenosyl-methionine (SAMe)
• Carnosine
• Theanine
• Palmitoylethanolamide (PEA)
• Tryptophan
• 5-hydroxytryptophan (5-HTP)

Other herbal products that may be useful for wound healing include the following:

• Oregano
• Lavender
• Honey
• Tea tree oil

Sources of St. John's Wort & What to Look For

St. John’s wort is not found in commercial food products in the United States. However, teas made from it are readily available.

It can be found as an OTC herbal supplement in many different formulations.

St. John’s Wort Supplements

St. John’s wort is widely available as a supplement in health food stores, groceries, pharmacies, and online. It can be purchased in many forms, such as:

• Tablets
• Capsules
• Tea
• Oil
• Tinctures
• Extracts
• Topical products

Look for products that have been third-party tested by one of the following agencies:

• U.S. Pharmacopeia (USP)
• ConsumerLab.com
• NSF.org

Quality testing from these companies does not assure safety or effectiveness.

Instead, the testing verifies that the ingredients listed on the package label match what is actually in the product and that the product is free of contaminants.

Summary

St. John’s wort is a flowering herb that may be an alternative to conventional antidepressants for mild to moderate depression, particularly for people not taking other medications.

It's essential to keep in mind, though, that just because some substances are natural doesn't mean it's safe. Do involve a healthcare provider in any treatment plan for depression.

St. John's wort can decrease the effects of many prescription medications, from birth control pills to heart medicines. Your provider can help you monitor for side effects and interactions.