St. John's Wort: Benefits for Mood, Usage and Drug Interactions

In short:

• St. John’s Wort (Hypericum perforatum) is a flowering plant most commonly used to ease symptoms of mild to moderate depression.
• The main active substances are hypericin and hyperforin, which act on mood-regulating neurotransmitters.
• Most important: St. John’s Wort can interact with many medicines, so always consult a doctor or pharmacist before using it.

St. John’s Wort is one of the best-studied herbal preparations, used for centuries to support mood and emotional well-being. In this article we review how it works in the body, what benefits it may offer, how to take it correctly and which medicines it must not be combined with.

What is St. John’s Wort?

St. John’s Wort (lat. Hypericum perforatum) is a perennial flowering plant with bright yellow, five-petalled flowers. It grows naturally in Europe, Asia and North America, and in Lithuania it is often found in meadows, roadsides and forest edges. The plant is named after St. John, because it traditionally blooms around late June – close to St. John’s Day.

For medicinal purposes the upper flowering part of the plant is used – the flowers and leaves. Extracts, capsules, teas and oil are made from them. In food supplements, St. John’s Wort extract is usually standardised by the amount of active substances – hypericin or hyperforin.

In various European countries this herb was used in folk medicine for many centuries – both internally and externally. In German it is called Johanniskraut, in English – St. John’s Wort; both names link the plant to the feast of St. John, when its flowers were traditionally collected.

How does St. John’s Wort work?

St. John’s Wort contains several biologically active compounds, the most important of which are hypericin, hyperforin and flavonoids. It is thought that mood is influenced by the combination of all these substances, not by one single compound.

The main mechanism of action of this herb is linked to the inhibition of the reuptake of the neurotransmitters serotonin, dopamine and noradrenaline. This means that these substances stay longer in the synaptic cleft and can act more strongly on the brain circuits that regulate mood. Some prescription antidepressants work on a similar principle, which is why combining St. John’s Wort with them is dangerous.

Researchers have found that hyperforin is considered the main mood-affecting substance, while hypericin and flavonoids most likely strengthen the overall effect.

Another important detail – these active substances do not reach the bloodstream immediately but build up gradually. This is exactly why the effect appears only after a few weeks, and why this herb should not be taken “as needed”, for example only when your mood drops.

St. John’s Wort benefits for mood

The best-studied benefit of St. John’s Wort is related to mood – specifically to symptoms of mild and moderate depression. Several reviews of clinical trials found that St. John’s Wort extract can be more effective than placebo and similar in effectiveness to some standard antidepressants, but with fewer side effects.

However, study results are not consistent. Some large, strictly controlled trials showed no advantage over placebo, which is why the U.S. Food and Drug Administration (FDA) has not approved St. John’s Wort as a treatment for depression. For this reason it is considered an additional rather than a primary measure, and it is not suitable for severe depression.

A more detailed, research-based overview of this herb is published by the U.S. National Institutes of Health Office of Dietary Supplements – NIH St. John’s Wort.

Interestingly, in many European countries – for example Germany – this herbal preparation is one of the natural remedies most often recommended by doctors for mild depression, where it is sold in pharmacies with a standardised composition. However, this does not mean it can be used without restrictions: even a natural remedy can have strong interactions.

It is important to have realistic expectations. If symptoms are severe, accompanied by thoughts of self-harm, or if depression makes it hard to work and maintain relationships, herbal preparations are not the right solution – urgent professional help is needed here. For milder mood swings a natural remedy can be a valuable part of support, but only as part of an overall approach: a healthy diet, exercise and sleep remain the foundation.

If you have been feeling low for more than two weeks, have lost interest, or have sleep problems, talk to a doctor first. Mood disorders require professional help, and St. John’s Wort can only be one of the measures a doctor considers alongside others.

St. John’s Wort for PMS and menopause symptoms

Beyond depression, this herb has also been studied for premenstrual syndrome (PMS) and menopause symptoms. Some small studies show that St. John’s Wort extract may help reduce mood swings, irritability and anxiety during PMS.

Similarly, during menopause this herb may relieve hot flushes and emotional discomfort for some women, although the evidence here is weaker. In these areas the results are preliminary, so St. John’s Wort should not be considered a primary measure for managing hormonal changes.

Although the mechanism is not fully clear, it is thought that the mood-stabilising effect may be useful during periods of hormonal fluctuation. Still, for these purposes other, better-studied supplements are often recommended, such as inositol or magnesium, so it is worth consulting a specialist about which option is most suitable for your situation.

St. John’s Wort benefits for sleep

This herb is not a direct sleep aid, but by improving your overall emotional state it can indirectly improve sleep quality too. Anxiety and low mood are often the main causes of poor sleep, so a mood-stabilising effect can also be reflected in calmer sleep.

However, if you are looking for something specifically for sleep, it makes more sense to choose dedicated sleep supplements, for example tryptophan, which is directly involved in the production of melatonin and serotonin.

In addition, this herb can slightly disturb sleep in some people, especially when taken late in the evening, so it is often advised to take it in the morning or during the day. If you notice restlessness, simply move your intake to an earlier time.

Other potential benefits of St. John’s Wort

This herb has also been studied in other areas. In the case of seasonal affective disorder (SAD), when mood worsens during the dark time of year, St. John’s Wort may be useful both alone and together with light therapy, although the evidence is limited.

St. John’s Wort oil is traditionally used topically on the skin – to soothe minor burns, wounds and irritation. Still, these applications are based mainly on traditional experience rather than large clinical trials.

In some studies this herb was also tried for nerve pain, for example in diabetic neuropathy, but the results do not yet give a solid basis for such recommendations. These applications are best regarded as experimental until larger confirming studies appear.

How to take St. John’s Wort?

The dose of this herb most often used in studies is 300 mg of standardised extract three times a day, 900 mg in total per day. The extract should be standardised to contain about 0.3 % hypericin or 3–5 % hyperforin.

This herb is sold on the market in various forms: capsules, tablets, tea, tincture and oil. Capsules with a standardised extract are the most convenient and best-studied option, because you know exactly how much of the active substances you are getting. Tea is suitable for milder daily use, but the concentration of active substances in it is lower and harder to predict.

It is recommended to take this herb regularly, every day at the same time, with or without food – as indicated on the package. The most important thing to know is that the effect does not appear immediately: most people notice an improvement only after 4–8 weeks of continuous use.

If you do not notice any improvement within 6–8 weeks, stop using it and consult a doctor. Do not exceed the dose indicated by the manufacturer, because higher doses increase the risk of side effects and phototoxicity rather than effectiveness.

Side effects and precautions

This herb is well tolerated by most people in the short term, but side effects are possible. The most common are digestive upset, dry mouth, dizziness, fatigue, restless dreams and increased sensitivity to sunlight.

Sensitivity to the sun, or phototoxicity, is especially relevant for people with fair skin and those taking high doses. When using this herb it is advisable to avoid prolonged sun exposure and tanning beds.

Pregnant and breastfeeding women should not use this herb, because there is not enough data on its safety during these periods. For children it is recommended only on a doctor’s advice.

It is not recommended to stop long-term use abruptly – it is better to reduce the dose gradually so the body can adapt. Also remember that this preparation can reduce the effectiveness of other medicines, so it is always worth informing your doctor or pharmacist about using it, even if you feel well.

Separately worth mentioning are people with bipolar disorder or a family history of the condition: some studies show that this herb can trigger a manic episode, so it is not recommended for such people without a specialist’s supervision.

St. John’s Wort interactions with medicines

This is the most important property of this herb to know before using it. St. John’s Wort stimulates the liver enzyme CYP3A4 and the transporter protein P-glycoprotein, so it speeds up the breakdown and removal of many medicines from the body. As a result, these medicines can work less effectively.

This herb can weaken the effect of the following medicines: oral contraceptives, the blood thinner warfarin, the immunosuppressant ciclosporin, the heart medicine digoxin, HIV medicines, cholesterol medicines and some cancer treatments.

The combination of St. John’s Wort with prescription antidepressants – selective serotonin reuptake inhibitors (SSRIs) or monoamine oxidase inhibitors (MAOIs) – is especially dangerous. Such a combination can cause serotonin syndrome – a dangerous condition with fever, confusion and heart rhythm disturbances.

If you take any prescription medicines, always consult a doctor or pharmacist before using this herb.

When planning surgery or anaesthesia it is also essential to tell your doctor if you have used this herbal preparation, because it can interact with anaesthetics and other medicines used during surgery. It is recommended to stop using it at least two weeks before planned surgery.

Frequently asked questions

Does St. John’s Wort help with depression?

St. John’s Wort can help ease symptoms of mild or moderate depression, but the evidence is mixed. In the case of severe depression it is not suitable – professional care and standard treatment are essential here.

How long does it take for St. John’s Wort to start working?

For most people the effect appears only after 4–8 weeks of regular use. It is not a fast-acting remedy, so it is important to be patient and not stop using it too early.

Can St. John’s Wort be used with contraceptive pills?

It is not recommended. St. John’s Wort can reduce the effectiveness of oral contraceptives and increase the risk of unplanned pregnancy. When using it, an additional method of protection should be used.

When is the best time to take St. John’s Wort – morning or evening?

There is no single rule. For some people this herb can disturb sleep, so if you notice restlessness, take it in the morning or during the day. The most important thing is to take it regularly at the same time.

Does St. John’s Wort cause side effects in the sun?

Yes, St. John’s Wort can increase the skin’s sensitivity to sunlight (phototoxicity). When using it, it is advisable to avoid prolonged sun exposure, especially for people with fair skin.

If you do not have St. John’s Wort preparations, other supplements can also help support mood and emotional balance. For example, tryptophan – the amino acid from which the body produces serotonin, or B vitamins, essential for normal nervous system function. For calmness, GABA – a neurotransmitter that helps you relax – is also often chosen.

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