St. John's wort: uses, benefits, side effects

“It’s natural—what could be wrong with it?” 

You’ve probably heard people say something along those lines about all sorts of plants and herbs used for a wide variety of purposes. But, as any healthcare professional can tell you, some of the most "natural" substances can cause serious harm if not used properly. 

St. John’s wort is one such substance. Scientists have extensively studied this ancient medicinal herb, and it’s been proven to be effective at treating a range of ailments. Still, natural does not equal non-toxic. St. John’s wort has side effects and can have serious drug interactions. 

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St. John’s wort (Hypericum perforatum) is a naturally growing plant found in Europe and Asia, with star-shaped, yellow flowers. It can also be called hypericum, goatweed, or Klamath weed (NCCIH, 2020). 

The plant is named for John the Baptist because St. John’s wort blooms in late June, around the time of the feast of St. John the Baptist (NCCIH, 2020).

The plant’s buds and flowers are dried, ground up, and made into a tea or placed into capsules. They can also be pressed into liquid form as oils or extracts.In some countries, healthcare professionals prescribe St. John’s wort as a ‘natural medicine’ to treat depression and other conditions. In the U.S., you can get St. John’s wort at any drug store as an herbal supplement. It’s important to know that the U.S. Food and Drug Administration (FDA) does not regulate herbal and dietary supplements the way they do prescription drugs and over-the-counter medications (Peterson, 2021). 

St. John’s wort has been used since ancient times for mental health conditions, including depression and insomnia. Herbal medicine practitioners have also used it for kidney and lung conditions and to help with wound healing (NCCIH, 2020). 

Today, St. John’s wort is used by some for a range of mental health conditions, including depression, attention-deficit hyperactivity disorder (ADHD), obsessive-compulsive disorder (OCD), and menopausal symptoms. St. John’s wort may also help treat bruises, muscle pain, and wounds when applied to the skin (Peterson, 2021). 

St. John’s wort can have potential side effects and interactions with other medications. Even though St. John’s wort may help with some of the following conditions, it’s crucial to speak with your healthcare provider before taking it.

Depression

Depression is when you feel low, sad, and lose interest in doing the things you love for at least two weeks. Symptoms can be classified as mild, moderate, or major depression. 

Several clinical trials suggest St. John’s wort may play a role in the treatment of depression. Multiple systematic reviews comparing a large number of studies showed that St. John’s wort appeared to reduce mild and moderate depressive symptoms compared to a placebo. It showed similar results to a prescription antidepressant, with fewer side effects than some prescription antidepressants. Specifically, it did not decrease libido (sex drive), a common side effect of many antidepressants (Apaydin, 2016; Ng, 2017). . 

Some studies have found that people who took St. John’s wort took it more often for the length of their prescribed treatment, compared to those taking antidepressants. Better adherence to this supplement could be because of St. John’s wort’s better side effect profile (Apaydin, 2016; Ng, 2017). 

In the studies, St. John’s wort seemed to work best for mild to moderate depression. There is a lack of data on how well it may work for severe depression. Overall, the reviews’ authors suggest interpreting the findings cautiously, as there was some variability in the studies. More research is needed to form a concrete understanding of the role St. John’s wort could play in treating depression.

Obsessive-compulsive disorder (OCD)

This mental health disorder is when a person has excessive thoughts that may lead to compulsive, repetitive behaviors. OCD is often challenging to treat effectively. There is limited but promising evidence that St. John’s wort may help in treating people with OCD. More research is needed (Peterson, 2021). 

Seasonal affective disorder

There is some slight evidence that St. John’s wort helps relieve some of the symptoms of seasonal affective disorder (SAD). SAD is a form of depression that happens in the winter months (Meester, 2016).

Menopause and premenstrual syndrome

In a small clinical trial, St. John’s wort seemed to help reduce hot flashes, a well-known and uncomfortable symptom of menopause (Al-Akoum, 2009).

Some people also use St. John’s wort for uncomfortable symptoms of premenstrual syndrome (PMS) like depression, PMS acne, pain, bloating, and irritability (Peterson, 2021).

Skin and other applications

St. John’s wort may be effective at relieving pressure sores (Yücel, 2017). Additional studies on inflamed skin have shown that oils and creams containing St. John’s wort may have anti-inflammatory properties (Arsić, 2011). 

St. John’s wort seems to also work for psoriasis. A double-blind placebo study showed that St. John’s wort was more effective in treating mild to moderate psoriasis than a placebo (Peterson, 2021).

Scientists aren’t exactly sure how St. John’s wort works, but several mechanisms have been proposed. The antidepressant effect of St. John’s wort seems to be due to the way it affects neurotransmitters or brain chemicals like serotonin, dopamine, and norepinephrine, similar to how some common antidepressant medications work (Peterson, 2021).

Some studies have shown that people who take St. John’s wort extracts report fewer side effects than with antidepressant medications. Those who do report side effects say they have dry mouth, fatigue, trouble sleeping, upset stomach, skin rashes, and irritability (Kasper, 2010). 

Although many studies indicate that St. John’s wort has a relatively low number of side effects, another more extensive study found that some people had these severe adverse effects (Apaydin, 2016): 

• Sudden high blood pressure (hypertensive crisis)

• Higher levels of thyroid-stimulating hormone

• Manic symptoms (behaving irritably or erratically)

• Increased sensitivity to sunlight (photosensitivity) 

People may think they don’t need to tell their healthcare provider that they take St. John’s wort because it’s considered a natural supplement. However, anything you put into your body is essentially a medication, whether it’s prescription or over-the-counter. In fact, St. John’s wort interacts with many medications and does have some risks, some with severe health consequences. 

Here are some common issues that may arise:

Serotonin syndrome

One of the most significant risks of taking St. John’s wort with certain medications is serotonin syndrome. 

St. John’s wort may help to balance the levels of neurotransmitters in the brain, including serotonin. Taking certain medications together with St. John’s wort raises serotonin levels in the brain, potentially leading to serotonin syndrome. Symptoms include a rapid heartbeat, high blood pressure, dilated pupils, sweating, and in some cases, very high fevers. It can be life-threatening. If you have any of these symptoms, seek immediate medical attention (Peterson, 2021).

The following medications can increase the risk of serotonin syndrome if you take them with St. John’s wort (Chrubasik-Hausmann 2019): 

• Selective serotonin reuptake inhibitors (SSRIs), such as paroxetine (Paxil), fluoxetine (Prozac), and sertraline (Zoloft) 

• Monoamine oxidase inhibitors (MAOIs) like phenelzine (Nardil) and tranylcypromine (Parnate) and the antidepressant amitriptyline (Elavil)

• Certain narcotics or pain medications like meperidine (Demerol), hydrocodone, morphine, or migraine pain relievers like sumatriptan (Imitrex) or zolmitriptan (Zomig) 

• Dextromethorphan, a common over-the-counter cough medication often found in cold/flu medicines like Robitussin DM

Decreased effectiveness

St. John's wort decreases or lowers the effectiveness of many medications. If you take any of these medications, be aware that they may not work as prescribed when taken with St. John's wort. In some cases, these medicines are essential for your health, and you cannot stop taking them. If you're taking one of these medications, it's important to avoid St. John's wort altogether. 

These essential medications include (Soleymani, 2017):

• Cyclosporine—taken to prevent organ rejection after transplantation

• Heart medications digoxin and ivabradine—taken to slow the heart rate down, so the heart pumps blood more efficiently

• HIV medications indinavir and nevirapine used in antiviral therapy

• Cancer medications irinotecan for metastatic colorectal cancer and imatinib are taken for myelogenous leukemia

• Coumadin (warfarin), a blood thinner or anticoagulant, to prevent strokes and heart attacks

• Cholesterol medications called statins that help lower your cholesterol, like simvastatin (Zocor) 

• Oral contraceptives or birth control pills

• Anti-anxiety pills including alprazolam (Xanax)

• Seizure medications like Dilantin

Pregnancy and breastfeeding

If you're trying to get pregnant, you may want to hold off on taking St. John's wort. 

A small study of John's wort taken in pregnancy found a slight increase in the number of babies born with malformations than what was expected (Kolding, 2015). The National Institute for Complementary and Integrative Health says St. John's wort has caused congenital abnormalities in laboratory animals. More evidence is needed to assess the complete safety profile of taking St. John's wort while pregnant (NICCH, 2020).

Older studies on breastfeeding when taking St. John's wort have noted that one component of the herb is found in breastmilk. The low levels of this component, named hypericin, are comparable to the level of antidepressants found in breast milk in women who take them. These levels appear to be safe for the baby (Klier, 2006). However, some mothers who take St. John's wort and breastfeed report their babies may be colicky, sleepy, and fussy (NICCH, 2020).

More research is needed to determine how safe St. John’s wort is for pregnancy and breastfeeding.

Skin sensitivity

Though a few studies indicate that St. John's wort can help with certain skin conditions like wounds, pressure sores, and psoriasis, there isn't a lot of information on how safe it is to use on the skin. St. John's wort can cause photosensitivity—an increased sensitivity to the sun—and severe skin reactions when you're out in the sun.

If you’re taking a medication that already has photosensitivity as a side effect, then taking it together with St. John’s wort can greatly increase your sensitivity to the sun and risk blistering sunburns. Some examples include antibiotics like ciprofloxacin, levofloxacin, and tetracycline (Soleymani, 2017).

Mental health conditions

St. John's wort can worsen or increase the symptoms of bipolar disorder and schizophrenia (Peterson, 2021).

Surgery

St. John’s wort may interfere with anesthesia drugs, causing excessive sedation and other complications during surgery. Your surgeon may ask you to stop taking it at least five days before your scheduled surgery (Wong, 2011).

Stopping St. John’s wort

There isn’t much research on how people feel when they stop taking St. John’s wort. Withdrawal symptoms may include anxiety, dizziness, and feeling sick. Rather than stopping St. John’s wort altogether, it may be best to work with your healthcare provider and reduce your dosage slowly to minimize any withdrawal symptoms.

St. John’s wort often comes as a tablet, capsule, tea, or liquid extract (Peterson, 2021). When taken as a supplement, the most common dosage is St. John’s wort extract of 0.3% hypericin content of 300 mg taken with meals three times a day.

The FDA does not regulate St. John's wort. This means the strength of the supplement listed on the bottle may not be the true strength of what's in the bottle, potentially decreasing the effectiveness or increasing the risk for side effects. Be sure to know the manufacturer of what you buy and only purchase from a reputable source.

While studies show St. John’s wort can treat mild to moderate depressive symptoms as well as antidepressants, this supplement interacts with many medications, over-the-counter drugs, and supplements. St. John’s wort can cause dangerous or even life-threatening effects. Before you take St. John’s wort or any other supplement, it is crucial to speak to your healthcare provider to make sure it is right for you.

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Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

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Current version

July 20, 2021

Written by

Tobi Ash, MBA, RN, BSN

Fact checked by

Steve Silvestro, MD

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About the medical reviewer

Steve Silvestro, MD, Ro

Dr. Steve Silvestro is a board-certified pediatrician and Associate Director, Clinical Content & Education at Ro.