St John’s wort: does it help depression, and is it safe?

What is St John’s wort?

St John’s wort is a plant, Hypericum perforatum, sold in products with different extracts and strengths. A study of one extract does not automatically establish the effects or quality of every bottle. How products are regulated also depends on the country and the claims made. In the United States, FDA has not approved it as an over-the-counter or prescription medicine for depression.

For a wider view of low mood and the different kinds of support available, start with stress and mood.24

What do studies of depression show?

The US National Center for Complementary and Integrative Health says some studies suggest benefit for mild-to-moderate depression, while results are less certain for severe depression and periods longer than 12 weeks. Trials differ in participants, extract and design. For example, a 1999 randomised study in moderate depression reported a greater improvement in symptom scores with a particular extract than with placebo over eight weeks. That finding does not establish that all products are equivalent or that the effect lasts. The study involved 263 people and was funded by the extract manufacturer, Steiner Arzneimittel.26

Why a negative trial needs careful interpretation

A 2002 US trial randomly assigned 340 adults with major depression to a St John’s wort extract, sertraline or placebo for eight weeks. Neither the extract nor sertraline differed significantly from placebo on the two primary outcomes. Because the established comparison medicine also did not separate from placebo on those measures, this particular trial has limited ability to distinguish effective from ineffective treatments. It did not establish the extract’s benefit in that population, but it does not settle every product or severity level.7

Interactions can be serious

St John’s wort can reduce the effectiveness of some medicines, including certain contraceptive pills, HIV medicines and transplant medicines. Other examples include the anticoagulant warfarin, some seizure medicines such as phenytoin and carbamazepine, and some cancer medicines. With certain antidepressants it can also increase the risk of serious serotonin-related effects. The exact products and medicines matter. Tell a pharmacist or prescriber what you take and ask before starting or stopping the herb or changing prescribed treatment. See supplement and medicine interactions.23

Some supplements can also affect serotonin. Memorial Sloan Kettering advises avoiding a combination of St John’s wort and 5-HTP because of the potential for excess serotonin. That warning is about a possible interaction, not a measure of how often harm occurs. If you already use both, ask a clinician or pharmacist promptly for advice. Read 5-HTP, sleep and interactions.11

Serotonin syndrome can be serious and may develop quickly. Symptoms can include agitation or confusion, sweating, fever, tremor or muscle spasms; these symptoms can have other causes too. If such symptoms occur after taking a medicine or supplement that affects serotonin, seek urgent medical help immediately and tell the care team about everything taken.1

Can it make contraception less effective?

St John’s wort can speed the breakdown of some contraceptive hormones and reduce effectiveness. In a small 2003 study, 18 people taking one combined oral contraceptive were studied with and without a particular St John’s wort extract. Researchers found lower blood exposure to one contraceptive hormone and more bleeding between periods; they did not find evidence of ovulation in that study. These measures are not a direct pregnancy rate, and the results do not quantify risk for every product or person. The interaction can persist after the herb is stopped. It can also matter for some emergency contraceptive pills: UK NHS guidance says to tell a doctor or pharmacist if taking St John’s wort when seeking emergency contraception. If pregnancy prevention may have been compromised, seek prompt local professional advice; options depend on the product, timing and circumstances. Do not assume that stopping the herb immediately restores protection.8910

When symptoms need attention

Depression can affect sleep, energy, concentration and daily life and can have different causes and degrees of severity. A clinician can help assess symptoms and discuss evidence-based care. Do not delay urgent local help if someone may harm themselves or is in immediate danger. This guide does not diagnose depression or recommend a product or dose.

The US NIH notes case reports of worsening psychotic symptoms in people with bipolar disorder or schizophrenia who took St John’s wort. It may also worsen anxiety in some people and can increase sensitivity to sunlight. Safety information in pregnancy and children is limited. NIH cautions that St John’s wort may be unsafe during pregnancy because it might increase the risk of birth defects; it also reports colic, drowsiness and lethargy in some breastfed infants whose mothers took it. Discuss use with a health professional when pregnant, breastfeeding or considering it for a child.45