What is the effect of St. John's wort?

St. John's wort is a herbal supplement that some individuals turn to for managing depression. People often choose St. John's wort as an alternative because many prescribed antidepressants come with significant side effects, and they hope a plant-based solution might have fewer adverse reactions.

Approximately 17 million Americans are affected by depression. Treatment options for depression include various methods, with antidepressant medications such as Prozac, Paxil, Elavil, and Nardil being commonly prescribed. Side effects from these medications may include insomnia, headaches, digestive issues, and changes in sexual drive or behavior. A 1994 study published in the British Medical Journal showed that St. John's wort was comparable to conventional antidepressants in effectiveness and outperformed placebo sugar pills in treating mild to moderate depression.

St. John's wort (hypericum perforatum) is a perennial shrub that produces yellow flowers. The plant's active ingredients are hypericin, pseudohypericin, and xanthones, though other elements may enhance the effects of these compounds. The extracts of St. John's wort are typically standardized to 0.3 percent hypericin. An average adult dosage is 300 milligrams taken three times a day, which provides 2.7 milligrams of hypericin daily.

The exact mechanism by which St. John's wort helps alleviate depression remains unclear. It is likely that hypericin works by boosting mood-regulating biochemicals in the brain, such as dopamine and serotonin, while also decreasing adrenal activity, which is typically heightened in depression. St. John's wort does come with potential side effects, including sensitivity to light, dry mouth, stomach discomfort, dizziness, and fatigue.

St. John's wort may assist in the treatment of certain retroviruses, including herpes, HIV, and the Friend leukemia virus, and could potentially aid in managing certain cancers. However, the evidence supporting its effectiveness for these conditions is not as strong or well-established as it is for depression.

Clinical trials are currently being conducted in the United States to assess the efficacy of St. John's wort for treating depression. Since St. John's wort is sold as a dietary supplement, it is not subject to regulation by the U.S. Food and Drug Administration. Any use of this supplement should be monitored by a healthcare provider. For a more detailed discussion on this subject, see How St. John's Wort Works.

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