Although some studies have reported benefits for more severe depression, others have not; for example, a large study sponsored by the National Center for Complementary and Integrative Health (NCCIH) found that the herb was no more effective than an inert pill (placebo) in treating major depression of moderate severity. A study co-funded by NCCIH and the National Institute of Mental Health found that neither St. John's wort nor a standard antidepressant medication relieved symptoms of minor depression better than a placebo.
St. John's wort may cause increased sensitivity to sunlight. Other side effects can include anxiety, dry mouth, dizziness, gastrointestinal symptoms, fatigue, headache, or sexual dysfunction.
Research shows that St. John's wort interacts with many medications in ways that interfere with their intended effects. Examples of medications that can be affected include:
- birth control pills
- cyclosporine, which prevents the body from rejecting transplanted organs
- digoxin, a heart medication
- indinavir and possibly other drugs used to control HIV infection
- irinotecan and possibly other drugs used to treat cancer
- seizure-control drugs, such as dilantin and phenobarbital
- warfarin and related anticoagulants
Taking St. John's wort with certain antidepressants may lead to increased serotonin-related side effects, which may be potentially serious.
St. John's wort is not a proven therapy for depression. If depression is not adequately treated, it can become severe. Anyone who may have depression should see a health care provider. There are effective proven therapies available.
Before taking any new medications, including natural health products, speak to your physician, pharmacist, or other health care provider. Tell your health care provider about any natural health products you may be taking.