Flowers of St. John’s Wort - Hypericum Perforatum (Hypericaceae)

Medicinal Use of St. John’s Wort – Hypericum Perforatum (Hypericaceae)

St. John’s wort flowers at the summer solstice. In medieval Europe it was considered to have the power to protect against ill health and evil influences. Medicinally it was thought to heal wounds and “all down-heartedness.” In the 19th century the herb fell into disuse, but recent research has brought it back into prominence as a key herb for nervous exhaustion and depression. It is now one of the most used herbal medicines in the world.

Habitat & Cultivation

St. John’s wort thrives in temperate regions worldwide. It prefers a sunny site and well-drained, chalky soil. It can be grown from seed or by root division in autumn. The flowering tops are harvested in summer.

Related Species

A number of other Hypericum species have a roughly similar medicinal action.

Key Constituents

  • Phloroglucinols (hyperforin)
  • Polycyclic diones (hypericin)
  • Flavonoids

Key Actions

  • Antidepressant
  • Anxiolytic
  • Antiviral
  • Wound healer
  • Anti-inflammatory


Depression: Clinical research since the 1970s has established St. John’s wort as an effective treatment for mild to moderate depression. A review in 2009 also concluded that the herb was helpful in treating severe depression. Research shows that St. John’s wort works on neurotransmitter levels (e.g. serotonin) in several different ways.

Viral infection: St. John’s wort extracts (particularly hypericin, the red pigment found in the petals and leaves) have strong antiviral activity, notably against influenza, herpes, and hepatitis B and C.

Safety: St. John’s wort rarely causes side effects itself, but it does interact with certain conventional medicines, mostly increasing the rate at which they are broken down by the liver. This changes the amount of the drug present in the bloodstream, significantly reducing its effectiveness. In rare situations, this can be life threatening.

Traditional & Current Uses

Nerve tonic: The herb acts as a restorative and neuroprotective, helping to reverse long-term nervous exhaustion and lowered mood. It can prove useful in seasonal affective disorder and chronic anxiety, and improves sleep quality.

Menopause: The herb is considered a specific for the lowered mood that can accompany menopause, often combined with black cohosh (Cimicifuga racemosa) in such cases.

Tissue healing: The red infused oil has potent wound-healing properties and historically has been used to heal knife and stab wounds. Nowadays, St. John’s wort oil is more commonly used to promote healing after surgery and minor burns. The oil can be particularly helpful in relieving neuralgia—shingles, sciatica, and toothache being common applications.