St John’s wort

Also known as Hypericum or Hypericum perforatum

St John’s wort is a herb and sold as a natural health product in New Zealand, at health food stores and pharmacies, for the treatment of depression and other conditions such as anxiety.

What is St John’s wort?

  • St John’s wort (also called Hypericum or Hypericum perforatum) is a herb and its flowers and leaves are used to make a plant product marketed for the treatment of depression and other conditions such as anxiety, menopause, pain. 
  • In New Zealand St John’s wort is not registered as a medicine but is considered a herbal supplement or complimentary medicine.
  • The mechanism of action of St John’s wort is not fully understood but it is believed to affect certain chemicals in the body such as serotonin and noradrenaline, and in this way is thought to improve mood. 
  • Many of the chemicals in St John's wort interacts with medicines used to treat depression and other illnesses. It is important to let your doctor or pharmacist know if you want to try St. John's wort so that he or she can check if it might interfere with other medicines you are taking.
  • There are no standardised St John's wort preparations in New Zealand. St John's wort is available in a variety of formulations such as tablets, capsules, liquid tinctures and teas.  

Does St John’s wort work?

Research has found that St. John's wort is useful in the treatment of mild to moderate depression, but not effective in severe depression.
  • In analyses of studies comparing St. John’s wort with placebo (sugar pills) and St. John’s wort with standard antidepressants (SSRIs or tricyclics), the authors found that compared with placebo, people taking St. John’s wort were more likely to experience an improvement in their symptoms. There were no significant differences in depression response rates between St. John’s wort and standard antidepressants. The studies also found that patients taking St. John’s wort were less likely to drop out of trials due to adverse effects than those taking standard antidepressants. 1,2

There are a number of products available on the market containing St. John's wort (Hypericum). When buying St. John's wort you should be careful about the potency (strength) and purity of the product. Standardised extract (0.3% Hypericum) has been well researched and proven in clinical trials.

St John's wort is possibly effective for menopausal symptoms, plaque psoriasis, wound healing and somatization disorder. Read more about St John's wort National Institute of Health.  


Because St John's wort is classified as a supplement, the strength and dose will vary depending on what brand of St John's wort you take. Always check the dosing instructions on the product label or packaging.  

The effect of St John's wort is not immediate. You may need to take it for two to three weeks before you notice any improvement. If there is no change in your symptoms by then, it’s likely St John's wort will not be of benefit for you and you should talk to your doctor about other ways of managing your symptoms.

Side effects

Side effects from St. John's wort are generally mild and include:

  • stomach upset
  • skin rash, hives or other skin rashes
  • feeling tired
  • restlessness
  • headache
  • dry mouth
  • feelings of dizziness or mental confusion.
  • skin - can become more sensitive to sunlight. If you have light skin and are taking St. John's wort, wear long sleeves and a hat when in the sun, and use a sunscreen with at least SPF 15 or higher.


Avoid sunlamps, tanning booths, and tanning beds.

Serotonin syndrome

  • You are at increased risk of serotonin syndrome if you recently started taking St John's wort, especially if you are already taking medicines that increase serotonin levels in the body such as the antidepressants selective serotonin reuptake inhibitors (SSRIs). 
  • Signs of serotonin syndrome include:
    • feeling agitated and restless,
    • heavy sweating,
    • shivering,
    • fast heart rate or irregular heart beat,
    • headache,
    • diarrhoea and
    • rigid or twitching muscles. 
  • Tell your doctor immediately or ring HealthLine 0800 611 116, if you experience these symptoms.


St John's wort interacts with a large number of medicines such as antidepressants, anticoagulants, and anticonvulsants. In most cases, St. John's wort makes the medicines less effective. In other cases, St. John's wort may make the effects of a medicine stronger. 

If you are being treated with any medicine, you should not use St. John's wort without first talking to your doctor or pharmacist. 

Learn more

The following links provide further information on St John's wort. Be aware that websites from other countries may contain information that differs from New Zealand recommendations.

Can I take St John's Wort with other medicines Medsafe, NZ
St John's wort Patient Info, UK
St. John's wort NHS Foundation Trust 
St John's wort  National Center for Complementary & Integrative Health Clearinghouse, USA


  1. Linde K, Berner MM, Kriston L. St John's wort for major depressionCochrane Database Syst Rev. 2008 
  2. Linde K, Berner MM, Kriston L. St John's wort for depression.Cochrane Database Syst Rev. 2005 

Credits: Sandra Ponen, Pharmacist. Reviewed By: Dr J Bycroft. Health Navigator NZ Last reviewed: 21 Oct 2015