Introduction

St. John’s wort is a plant with yellow flowers that has been used for centuries for health purposes, such as for depression and anxiety. This fact sheet answers some frequently asked questions about St. John’s wort and depression, and summarizes what the science says about its effectiveness and the research being done.

Key Points

  • Studies suggest that St. John’s wort is of minimal benefit in treating major depression. A study cofunded by the National Center for Complementary and Alternative Medicine (NCCAM) found that St. John’s wort was no more effective than placebo in treating major depression of moderate severity. There is some scientific evidence that St. John’s wort is useful for milder forms of depression.
  • St. John’s wort interacts with certain drugs, and these interactions can limit the effectiveness of some prescription medicines.
  • St. John’s wort is not a proven therapy for depression. If depression is not adequately treated, it can become severe and, in some cases, may be associated with suicide. Consult a health care provider if you or someone you care about may be experiencing depression.
  • Tell your health care providers about any complementary and alternative practices you use. Give them a full picture of what you do to manage your health. This will help ensure coordinated and safe care.

About St. John’s Wort

St. John’s wort (Hypericum perforatum) is a long-living plant with yellow flowers whose medicinal uses were first recorded in ancient Greece. It contains many chemical compounds. Some are believed to be the active ingredients that produce the herb’s effects, including the compounds hypericin and hyperforin.

How these compounds actually work is not yet fully understood, but several theories have been suggested. Preliminary studies suggest that St. John’s wort might work by preventing nerve cells in the brain from reabsorbing the chemical messenger serotonin, or by reducing levels of a protein involved in the body’s immune system functioning. St. John’s wort has been used over the centuries for mental conditions, nerve pain, and a wide variety of other health conditions. Today, St. John’s wort is used for anxiety, mild to moderate depression, and sleep disorders.

In Europe, St. John’s wort is widely prescribed for depression. In the United States, there is public interest in St. John’s wort as a treatment for depression, but it is not a prescription medicine; it is, however, one of the most commonly used herbal supplements.

In the United States, St. John’s wort products are sold as:

  • Capsules and tablets
  • Teas—the dried herb is added to boiling water and steeped
  • Liquid extracts—specific types of chemicals are removed from the herb, leaving the desired chemicals in a concentrated form.

About Depression

Depression is a medical condition that affects nearly 21 million American adults each year, according to the National Institute of Mental Health. Mood, thoughts, physical health, and behavior all may be affected. Symptoms of depression commonly include:

  • Persistent sad, anxious, or “empty” feelings
  • Feelings of hopelessness and/or pessimism
  • Feelings of guilt, worthlessness, and/or helplessness
  • Restlessness or irritability
  • Loss of interest or pleasure in activities that the person once enjoyed
  • Fatigue and decreased energy
  • Difficulty concentrating, remembering details, and/or making decisions
  • Insomnia, early–morning wakefulness, or excessive sleeping
  • Overeating, or appetite loss
  • Thoughts of suicide, suicide attempts
  • Persistent aches or pains, headaches, cramps, or digestive problems that do not ease with treatment.

Depression comes in several forms and its symptoms and severity can vary from person to person. For example:

  • In major depression (also called major depressive disorder), people experience symptoms that interfere with their ability to work, study, sleep, eat, and take pleasure in activities they once enjoyed. Symptoms last for at least 2 weeks but frequently last for several months or longer.
  • In dysthymia (also called dysthymic disorder), a less severe, but more chronic form of depression, people experience symptoms that are not as disabling but keep them from functioning well or feeling good. Symptoms last at least 2 years. Many people with dysthymia also have episodes of major depression.
  • In bipolar disorder (also called manic–depressive illness), people have periods of depressive symptoms that alternate or may co-exist with periods of mania. Symptoms of mania include abnormally high levels of excitement and energy, racing thoughts, and behavior that is impulsive and inappropriate.

In addition, milder forms of depression exist that fall into the category of minor depression. In minor depression, people experience the same symptoms as major depression, but they are fewer in number and are less disabling. Symptoms last at least 6 months but less than 2 years continuously.

Depression can be treated effectively with conventional medicine, including antidepressants and certain types of psychotherapy.

What the Science Says About St. John’s Wort for Depression

Scientific evidence regarding the effectiveness of St. John’s wort for depression is inconsistent. An analysis of the results of 37 clinical trials concluded that St. John’s wort may have only minimal beneficial effects on major depression. However, the analysis also found that St. John’s wort may benefit people with minor depression; these benefits may be similar to those from standard antidepressants. Overall, St. John’s wort appeared to produce fewer side effects than some standard antidepressants.

One of the studies included in the analysis was cofunded by NCCAM and two other components of the National Institutes of Health (NIH)—the National Institute of Mental Health and the Office of Dietary Supplements. This study found that St. John’s wort was no more effective than placebo in treating major depression of moderate severity. However, the antidepressant sertraline, used in one arm of the study, also showed little difference from placebo.

Side Effects and Risks

The most common side effects of St. John’s wort include dry mouth, dizziness, diarrhea, nausea, increased sensitivity to sunlight, and fatigue.

Research has shown that taking St. John’s wort can limit the effectiveness of some prescription medicines, including:

  • Antidepressant medicines
  • Birth control pills
  • Cyclosporine, a medicine that helps prevent the body from rejecting transplanted organs
  • Digoxin, a medicine used to strengthen heart muscle contractions
  • Indinavir and other medicines used to control HIV infection
  • Irinotecan and other anticancer medicines
  • Warfarin and related medicines used to thin the blood (known as anticoagulants)

When combined with certain antidepressants, St. John’s wort also may increase side effects such as nausea, anxiety, headache, and confusion.