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Shelton, however, stood his ground. He organized the study after seriously depressed patients, who had taken St. John's wort but hadn't been helped by it, began turning up en masse at his office. Learning that other psychiatrists were encountering a similar influx, he recruited doctors at nearly a dozen medical centers to join him in a clinical trial of the effectiveness of St. John's wort in combatting depression. With unrestricted funding from Pfizer, which makes both the prescription antidepressant Zoloft and an extract of St. John's wort, the doctors recruited 200 subjects, nearly two-thirds of them women in their 40s. All had suffered from major depression for at least four weeks. Some found it difficult to get out of bed or care for their children.
Blindly assigned to one of two groups, they were given either a placebo or St. John's wort. The initial dose: three standard 300-mg tablets a day, which was upped to four tablets if there was no improvement after four weeks. Although the St. John's wort group showed slightly more improvement than the placebo group (27% v. 19%) at the end of the eight-week trial, the doctors regarded the difference as statistically insignificant. When taking prescription antidepressants, two-thirds of patients improve.
Shelton and his colleagues acknowledge that theirs is not the final word. That could come before the end of the year when the National Institutes of Health completes a larger, three-year study that will meet one of the criticisms of the Vanderbilt trial. Instead of simply dividing patients into two groups--one on St. John's wort, the other on a placebo--the NIH study has a third group taking a prescription antidepressant. What should people who are using St. John's wort or thinking about it do until then? "Hold off," says Shelton, and consider one of the nearly two dozen prescription medications whose effectiveness has been proved.