Less than a day after members of the American Association for Cancer Research were informed that St. John's Wort may interfere with the effects of a common cancer drug, researchers from Duke University Medical Center released a study indicating that the popular herbal supplement may be ineffective in treating cases of major depression.
In the study, headed by Dr. Jonathan Davidson, physicians treated 340 patients for eight weeks with a daily dosage of St. John's Wort, the antidepressant Zoloft, or a placebo. The patients were unaware of which medication they were receiving.
If a patient responded to the treatment, he or she entered into an eighteen-week continuation phase. According to the report, at the end of the clinical trial the effectiveness of St. John's Wort was shown to be minimal. Supporters of the supplement claim it is designed only for milder forms of depression.