Real evidence for low mood — but one of the most interaction-prone supplements, especially with the pill and antidepressants.
St John's Wort is a herb with real evidence for lifting mild-to-moderate low mood, sometimes used by women for mood dips around the menstrual cycle or menopause. It works on brain chemicals including serotonin. But it is also one of the most interaction-prone supplements sold — and that has to come first in any honest discussion.
For mild-to-moderate depression, the evidence is good — in trials it can perform comparably to standard antidepressants. The problem isn't whether it works; it's what it does to your other medicines. For most women, the safety issues outweigh the convenience, and a safer option like saffron is a better first choice for premenstrual mood.
Mild-to-moderate low mood — but only after reviewing every medication you take with a pharmacist or doctor.
Trials use a standardised extract, often 300 mg three times a day. Because of the interactions, it should only be used under medical supervision, not self-started.
With meals, in divided doses. Effects on mood build over several weeks.
It increases sun sensitivity (easier sunburn), and can cause stomach upset or dry mouth.
Nothing — because of its interaction profile, it should not be casually combined with other supplements or medicines.
This is the crucial part. St John's Wort speeds up a major drug-processing enzyme (CYP3A4). It can make hormonal contraception fail, risking unplanned pregnancy, and weaken many drugs. Combined with antidepressants (SSRIs) it can cause serotonin syndrome, a medical emergency. It also affects warfarin, some HIV and transplant medicines, and more.
Anyone on the contraceptive pill, antidepressants, or any prescription medication — which is most people. Avoid in pregnancy.
A standardised extract (often to 0.3% hypericin) — but only obtained and used with a doctor's oversight.
St John's Wort genuinely helps mild low mood, but its interactions — especially with the contraceptive pill and antidepressants — make it one to use only under medical supervision. For premenstrual mood, saffron is a far safer first choice.
Cochrane review of St John's Wort for depression; NHS and NCCIH guidance on St John's Wort interactions; reports on contraceptive failure and serotonin syndrome.
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Based on guidance from the NHS, NICE, Cleveland Clinic and peer-reviewed research.
General information, not a substitute for personal medical advice — always consult your doctor or a qualified health professional before making health decisions. If you are pregnant, breastfeeding, trying to conceive, under 18, or taking medication, speak to your doctor before starting any supplement.