What is St. John's wort?

St. John's wort (Hypericum perforatum) is a plant with yellow flowers that people in European countries have used for centuries to treat mild to moderate depression. In Canada, it is sold as a dietary supplement and can be found at health food stores and pharmacies.

What is St. John's wort used for?

St. John's wort is used in the short-term treatment of mild to moderate depression. One study found that St. John's wort may also be effective in treating moderate to severe major depression.¹

It may take up to 2 to 3 weeks for St. John's wort to improve depressive symptoms. Not all preparations of St. John's wort are the same. A standardized form means the amount of St. John's wort is the same in every capsule.

Is St. John's wort safe?

St. John's wort causes fewer side effects (such as digestive discomfort or headaches) than antidepressant medicines, although it may cause a rash with sun exposure.

St. John's wort may interact with medicines used to treat some other illnesses, such as AIDS. 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 determine whether it might interfere with other medicines you are taking.

• Do not take St. John's wort while you are taking other antidepressants. You may overmedicate yourself, resulting in serious negative side effects. Always talk with your doctor before you take any herbal remedies to treat depression or other conditions.
• Do not take St. John's wort while you are taking protease inhibitors (PIs) or nucleoside reverse transcriptase inhibitors (NRTIs) for the treatment of HIV infection.
• Do not take St. John's wort while you are pregnant or breast-feeding.

The Natural Health Products Directorate (NHPD), within the Health Products and Food Branch of Health Canada, regulates dietary supplements in Canada. Dietary supplements, including St. John's wort, must be reviewed and approved by the NHPD before they can be sold in Canada.

Always tell your doctor if you are using a dietary supplement or if you are thinking about combining a dietary supplement with your conventional medical treatment. It may not be safe to forgo your conventional medical treatment and rely only on a dietary supplement. This is especially important for women who are pregnant or breast-feeding.

When using dietary supplements, keep in mind the following:

• Like conventional medicines, dietary supplements may cause side effects, trigger allergic reactions, or interact with prescription and non-prescription medicines or other supplements you are taking. A side effect or interaction with another medicine or supplement may make other health conditions worse.
• Dietary supplements may not be standardized in their manufacturing. This means that how well they work or any side effects they cause may differ among brands or even within different lots of the same brand. The form you buy in health food or grocery stores may not be the same as the form used in research.
• The long-term effects of most dietary supplements, other than vitamins and minerals, are not known. Many dietary supplements are not used long-term.