St. John’s wort (Hypericum perforatum) is a flowering plant native to Europe, western Asia, and northern Africa. You can spot it by its bright yellow flowers, which bloom around late June. The name comes from St. John the Baptist, since the flowering period traditionally coincides with his feast day on 24 June. “Wort” is simply an old English word for plant.

People have been using St. John’s wort medicinally for at least 2,000 years. The ancient Greeks used it for wound healing and as a diuretic. In medieval Europe, it gained a reputation as protection against evil spirits. These days, the interest is far more practical: can this plant actually help with depression and other health problems?

I’ve gone through the clinical evidence to see what holds up. The short answer is that St. John’s wort does have some genuine uses, particularly for mild-to-moderate depression, but it comes with serious caveats that don’t get enough attention.

What is in St. John’s wort?

The plant contains several active compounds. The two that get the most attention are hypericin and hyperforin. Hypericin gives the plant extract its characteristic reddish colour and was initially thought to be the main active ingredient. More recent research suggests hyperforin may actually be more important for the antidepressant effects [1].

St. John’s wort extracts also contain flavonoids like quercetin and rutin, plus various phenolic acids. The problem for researchers is that these compounds work together in ways that aren’t fully understood. Isolating any single compound often produces weaker effects than the whole extract [2].

Most supplements are standardised to contain a specific percentage of hypericin (usually 0.3%) or hyperforin (usually 3-5%). This standardisation matters because the composition varies widely depending on where the plant was grown, when it was harvested, and how the extract was prepared.

Benefit 1: Depression (mild to moderate)

This is by far the most common use for St. John’s wort, and it’s where the evidence is strongest. But “strongest” doesn’t mean “simple.”

A 2016 meta-analysis looked at 27 clinical trials comparing St. John’s wort to either placebo or standard antidepressants (SSRIs like fluoxetine, sertraline, and paroxetine). The analysis included 3,808 participants with mild-to-moderate depression [3].

The findings were actually quite favourable: St. John’s wort performed comparably to SSRIs for mild-to-moderate depression. Response rates were similar, and Hamilton Depression Rating Scale (HAM-D) scores improved to roughly the same degree. What made the herbal treatment look particularly good was the side effect profile. People taking St. John’s wort were less likely to drop out of trials due to adverse effects than those taking conventional antidepressants.

Here’s where I need to be honest about the limitations. Most positive trials were conducted in German-speaking countries, where St. John’s wort has a long tradition and regulatory approval. Some larger trials conducted in the US found no benefit over placebo for major depression [4]. This geographical discrepancy has never been satisfactorily explained. It could be differences in patient selection, extract preparation, dosing, or even publication bias.

The other major caveat: St. John’s wort takes time to work. You’re looking at 4-6 weeks before seeing meaningful improvement, similar to prescription antidepressants. It’s not a quick fix, and it’s not appropriate for severe depression or anyone experiencing suicidal thoughts. If depression is significantly interfering with your ability to function, or if you’re having thoughts of self-harm, please see a doctor immediately.

The NHS guidance on St. John’s wort confirms its use for mild depression but emphasises the drug interaction risks (more on this below).

Benefit 2: Menopausal symptoms (particularly hot flushes)

Hot flushes affect roughly 75% of women going through menopause. Most women experience them for a year or two, but about 15% continue to have them for decades. The standard treatment is hormone replacement therapy (HRT), but not everyone can or wants to take hormones [5].

A 2010 double-blind trial looked at 100 women (average age 50) experiencing menopausal symptoms. Over 8 weeks, those taking St. John’s wort reported reduced severity and frequency of hot flushes compared to placebo [6]. The effect wasn’t dramatic, but it was statistically significant.

Why might this work? Nobody’s entirely sure. One theory is that St. John’s wort affects serotonin signalling, and serotonin plays a role in thermoregulation. SSRIs (which increase serotonin availability) are sometimes prescribed off-label for hot flushes, so this mechanism isn’t implausible.

I wouldn’t put too much weight on this single trial. The sample size was modest, and larger studies haven’t been conducted. If you’re dealing with severe menopausal symptoms, there are better-studied options available. But for mild hot flushes in someone who wants to avoid hormones and prescription drugs, St. John’s wort might be worth discussing with a doctor.

For more information on managing menopausal symptoms, see our article on health foods for menopause.

Benefit 3: Somatoform disorders

Somatoform disorders, now generally called somatic symptom disorders, are conditions where people experience physical symptoms that can’t be fully explained by a medical diagnosis. These are real symptoms causing real distress, not “imagined” illness.

A 6-week trial involving 184 participants with somatoform disorders (excluding those with major depression) found that St. John’s wort extract improved symptoms significantly more than placebo. The response rate was 45.4% in the treatment group versus 20.9% for placebo [7].

This makes some biological sense. Many somatoform conditions have connections to anxiety and depression, and St. John’s wort’s effects on neurotransmitter systems could potentially help. The authors suggested it might be a reasonable option for patients with mild-to-moderate somatoform symptoms.

One study isn’t definitive, and this isn’t a common use for St. John’s wort. But it’s an interesting finding that deserves more research attention.

Benefit 4: Wound healing

Traditional use of St. John’s wort included topical application for wounds and burns. Modern research has started to examine whether there’s anything to this.

A 2010 trial looked at 144 women who had undergone caesarean section. Those who applied St. John’s wort extract cream to their surgical wounds had faster healing and reduced scarring compared to placebo. Pain and itching during the healing process were also reduced [8].

The mechanism may involve flavonoids in the extract stimulating fibroblast production and collagen synthesis. Essentially, it might speed up the normal wound healing process.

This is topical use, which is quite different from taking oral supplements. The risk of drug interactions (discussed below) is much lower with topical application since systemic absorption is minimal. If you’re interested in wound healing, this is probably the safest way to use St. John’s wort.

Side effects and safety concerns

At normal doses taken for less than 12 weeks, St. John’s wort is generally well-tolerated. Common side effects include:

Difficulty sleeping (insomnia)
Vivid dreams
Dry mouth
Dizziness
Headache
Diarrhoea or stomach upset
Fatigue or restlessness
Skin rash

Most of these are mild and often improve with continued use. However, there’s one side effect that deserves special attention: photosensitivity.

Photosensitivity

St. John’s wort can make your skin more sensitive to sunlight. This condition, called photodermatitis, can cause rash, blistering, or burns after sun exposure that wouldn’t normally cause problems. People with fair skin are at higher risk.

If you’re taking St. John’s wort, limit sun exposure and use sunscreen. This is particularly important if you’re also taking other medications known to cause photosensitivity.

Safety precautions and contraindications

This is where things get serious. St. John’s wort interacts with a genuinely alarming number of medications. If you take any prescription drugs, you need to discuss St. John’s wort with your doctor or pharmacist before using it.

Who should avoid St. John’s wort:

Pregnant or breastfeeding women: Safety hasn’t been established, and there’s theoretical concern about effects on foetal development.
People with liver or kidney dysfunction: The extract is metabolised by the liver and excreted by the kidneys. Impaired function could lead to accumulation.
Anyone scheduled for surgery: Stop taking St. John’s wort at least 2 weeks before any surgical procedure. It may interfere with anaesthetic drugs and affect bleeding.
People with bipolar disorder: St. John’s wort may trigger manic episodes in people with bipolar disorder or a history of mania.
People with severe depression or psychosis: This is not appropriate treatment for serious psychiatric conditions.

Drug interactions:

St. John’s wort induces cytochrome P450 enzymes in the liver, which speed up the metabolism of many drugs. This can make medications less effective, sometimes dangerously so. It also affects P-glycoprotein transporters, further altering drug levels.

Medications with significant interactions include:

Antidepressants: Combining St. John’s wort with SSRIs, SNRIs, or MAOIs can cause serotonin syndrome, a potentially life-threatening condition. Never combine them.
Oral contraceptives: St. John’s wort can reduce the effectiveness of birth control pills, leading to unintended pregnancy.
HIV medications: Reduces blood levels of protease inhibitors and non-nucleoside reverse transcriptase inhibitors.
Immunosuppressants: Ciclosporin and tacrolimus levels can drop dramatically, risking organ rejection in transplant patients.
Blood thinners: Affects warfarin metabolism, requiring dose adjustments.
Heart medications: Reduces effectiveness of digoxin.
Sedatives and sleeping pills: Can alter effectiveness of benzodiazepines and other sedatives.
Anticonvulsants: May reduce blood levels of some epilepsy medications.
Cancer chemotherapy: Can reduce the effectiveness of certain chemotherapy drugs.

The Mayo Clinic page on St. John’s wort maintains a comprehensive list of drug interactions. If you take any medications, check this before using St. John’s wort.

Other conditions requiring caution:

ADHD: May worsen symptoms of inattention
Dementia: May worsen cognitive symptoms
Schizophrenia: May worsen psychotic symptoms
Infertility: Animal studies suggest it may interfere with conception

How St. John’s wort is taken

Standard dosing for depression is typically 300mg of standardised extract taken three times daily (total 900mg/day). Extracts are usually standardised to 0.3% hypericin or 3-5% hyperforin.

Effects take 4-6 weeks to become noticeable. This isn’t a supplement you take occasionally when feeling low. It requires consistent daily use over an extended period.

For topical use (wounds, burns), creams and oils containing St. John’s wort extract are applied directly to the affected area.

The bottom line

St. John’s wort has genuine evidence supporting its use for mild-to-moderate depression, roughly comparable to prescription SSRIs with fewer side effects. That’s not nothing. For the right person, it might be a reasonable option.

But “the right person” excludes quite a lot of people. If you take any prescription medications, the interaction risk is serious. If your depression is severe, this isn’t appropriate treatment. If you might become pregnant, it could interfere with your contraception.

The other traditional uses have less evidence behind them. Menopausal hot flushes, somatoform disorders, and wound healing all have some preliminary support, but not enough for strong recommendations.

If you’re considering St. John’s wort, talk to a healthcare professional first. This is one supplement where the drug interaction potential genuinely matters, and a pharmacist or doctor can check whether it’s safe given your specific situation.

References

Butterweck V, Schmidt M. St. John’s wort: role of active compounds for its mechanism of action and efficacy. Wien Med Wochenschr. 2007;157(13-14):356-61.
Nahrstedt A, Butterweck V. Biologically active and other chemical constituents of the herb of Hypericum perforatum L. Pharmacopsychiatry. 1997;30 Suppl 2:129-34.
Ng QX, Venkatanarayanan N, Ho CY. Clinical use of Hypericum perforatum (St John’s wort) in depression: A meta-analysis. J Affect Disord. 2017;210:211-221.
Hypericum Depression Trial Study Group. Effect of Hypericum perforatum (St John’s wort) in major depressive disorder: a randomized controlled trial. JAMA. 2002;287(14):1807-14.
Stearns V, Beebe KL, Iyengar M, Dube E. Paroxetine controlled release in the treatment of menopausal hot flashes: a randomized controlled trial. JAMA. 2003;289(21):2827-34.
Abdali K, Khajehei M, Tabatabaee HR. Effect of St John’s wort on severity, frequency, and duration of hot flashes in premenopausal, perimenopausal and postmenopausal women: a randomized, double-blind, placebo-controlled study. Menopause. 2010;17(2):326-31.
Müller T, Mannel M, Murck H, Rahlfs VW. Treatment of somatoform disorders with St. John’s wort: a randomized, double-blind and placebo-controlled trial. Psychosom Med. 2004;66(4):538-47.
Samadi S, Khadivzadeh T, Emami A, Moosavi NS, Tafaghodi M, Behnam HR. The effect of Hypericum perforatum on the wound healing and scar of cesarean. J Altern Complement Med. 2010;16(1):113-7.