The celebrated herbal supplement St. John's wort did not help seriously depressed patients feel any better than did a dummy pill in the most rigorous study yet of the widely promoted pill.
The study, published today in the Journal of the American Medical Assn., is expected to stir controversy among medical scientists and natural health practitioners about the natural remedy, which millions of Americans have turned to with or without their doctors' consent.
"We conclude that there currently is no credible evidence to support the efficacy of St. John's wort for people with depression," wrote the study's researchers, who worked at 11 different medical centers and were led by Dr. Richard Shelton, a psychiatrist at Vanderbilt University.
Shelton has been an outspoken critic of prior studies of St. John's wort, saying that they were too small or sloppily conducted to withstand scientific scrutiny. His new findings only strengthen his conviction, he said.
But some researchers and herbal trade representatives cautioned against over-interpreting the study. Although it may be the most scientifically careful and among the largest so far, it doesn't invalidate the more than two dozen rather modest studies suggesting the herb may help lift depression in some people, they said.
"You have to remember that with any single study, you can't immediately assume that the findings apply directly to you as an individual," said Dr. David Feinberg, a UCLA psychiatrist.
"This study gives us valuable information, but it doesn't mean you should necessarily throw your St. John's wort out," he said. Still, he added, the new research was impressive and should spark more inquiry.
In the eight-week study of 200 adults with serious depression, the medical researchers gave a validated commercial St. John's wort extract to half of them and a look-alike, taste-alike dummy pill to the rest.
Neither the researchers nor the patients knew which pills were real until afterward. Overall, the people given the herb felt no better than those taking the placebo.
Outside researchers praised the study because it was larger and more objective than previous ones and involved patients whose depression was more clearly defined.
The rigorous use of a placebo was especially important in the study, researchers say, because people with depression sometimes feel better simply as a result of medical attention. Shelton and others have said such a placebo effect may partly explain why previous studies of St. John's wort appeared to relieve depression.
The new study does not rule out the possibility that St. John's wort may improve low moods that don't qualify as major depression, which is defined as a state that persists for at least two weeks and has other effects, such as disrupting appetite, sleep or work and prompting thoughts of death.