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Updated September 22, 2015.

What Is St. John's Wort?

St. John's wort, or Hypericum perforatum, is a small shrub with clusters of yellow flowers which grows mainly in Europe, Asia and North America.

It has a long history of use as a depression remedy, going back to the time of ancient Greece. In modern times, it has gained increasing support in the medical literature as an effective treatment for mild to moderate depression and is quite popular in both the U.S.


and Europe.

All growing parts of the plant above the soil are used to manufacture the herbal extract, which is used medicinally in a variety of forms, such as pills, capsules, teas and tinctures.

How Does It Work?

It is unknown exactly how St. John's wort relieves depression, but there are two substances which are believed to be its main active components: hypericin and hyperforin.

It has been proposed that hypericin may act upon the brain in ways that decrease production of the stress hormone cortisol, while increasing the availability of neurotransmitters such as serotonin, norepinephrine and dopamine.

Hyperforin may also work by increasing the availability of these mood-regulating substances, as well as others, but serotonin is thought to be the most important neutrotransmitter affected.

Other components of St. John's wort, such as the flavonoids, act as irreversible monoamine oxidase-A inhibitors, but their concentrations are so low that they are not likely to be involved in the antidepressants effect of St.

John's wort.

Effectiveness

The medical literature seems to suggest that St. John's wort is most effective for those with mild to moderate depression. However, it may be less effective for those with more severe or chronic depression.

Safety and Tolerability

The side effects that have been reported with St. John's wort are both uncommon and mild, when they do occur. Some of the reported side effects include: dry mouth, dizziness, constipation, gastrointestinal symptoms and confusion.

Rarely, patients will report an increased sensitivity to light with St. John's wort, especially at higher doses. Some scientists have recommended the precautionary use of sunscreen for patients spending a large amount of time in the sun.

At least 17 cases of psychosis, 12 of which were comprised of mania or hypomania, have been reported in the literature. Bipolar patients are advised to use St. John's wort only if they are also taking a mood stabilizer.

If you are taking any other medications, you should consult with your doctor or pharmacist about the possibility of any drug interactions with St. John's wort. Several drugs - including warfarin, cyclosporin, birth control pills, theophylline, phenprocoumon, digoxin, indivir and irinotecan - may potentially become less effective if taken in conjunction with St. John's wort. HIV-positive patients who take a protease inhibitor, cancer patients receiving chemotherapy and transplant patients receiving immunosuppressive drugs should be especially cautious about using St. John's wort. It is also recommended that St. John's wort not be combined with SSRIs due to anecdotal reports of serotonin syndrome, perhaps due to the monoamine oxidase inhibitor activity of St. John's wort.

Pregnancy and Breastfeeding

Little is known about what effects St. John's wort may have during pregnancy and breastfeeding. It is advised that women who are pregnant or intend to become pregnant should avoid St. John's wort until more complete safety data is available.

<sub>Sources:

"St. John's Wort."  NIH National Center for Complementary and Integrative Health.  U.S. Department of Health and Human Services.  Accessed:  September 5, 2015.</sub>