The herbal supplement St. John's wort is no more effective at treating moderately severe depression than a placebo is, according to a new study. The findings, published today in the Journal of the American Medical Association, indicate that patients suffering from depressive symptoms should not substitute the herbal remedy for clinical care.

Jonathan R.T. Davidson of Duke University Medical Center and colleagues tested the effects of an extract of Hypericum perforatum (St. John's wort) known as LI-160 against both a placebo and the antidepressant medication Zoloft. The researchers tracked 340 patients suffering from clinically diagnosed, moderately severe depression for a minimum of eight weeks and randomly assigned them a treatment strategy. Neither the patients nor the doctors knew which medication subjects took. According to the report, after eight weeks, St. John's wort showed no benefits over placebo for treating depression. But because Zoloft was also not significantly different than a placebo on the primary measure of the study, the results were far from straightforward. Patients taking Zoloft did show improvement on one of three scales used to indicate the severity of symptoms, whereas H. perforatum had no efficacy on any measure. "Rather than self-medicate with an over-the-counter medication or supplement, patients are strongly advised to consult an appropriate healthcare provider to assess the best treatment for a depressive episode," Davidson notes.

Though the study focused on one well-characterized extract of St. John's wort, many are marketed and the active ingredient of H. perforatum remains unclear. Study co-author Robert Califf of the Duke Clinical Research Institute cautions that "as long as these types of products remain available to the public without the protections of adequate, controlled and unbiased studies, taking them is like playing Russian roulette with your health." The authors conclude that St. John's wort should not be used in place of proven clinical methods, including therapy, to treat moderate depression.