Controlled clinical trials of hypericum extracts in depressed patients--an overview

In Germany, hypericum extracts are among the most widely prescribed antidepressants. Additionally, many preparations of St. John's wort are sold on the free market and one extract is even the best selling antidepressant in the country. In contrast to synthetic antidepressants, the approval procedures are not so strict, which implies that the pharmaceutical industry is not forced to conduct clinical trials suitable for licensing. Nevertheless, numerous studies on hypericum extracts including depressed patients have been published in the last 20 years. The purpose of this paper is to review these investigations in respect of methodological considerations and to draw conclusions pertaining to the proof of antidepressant efficacy. To this effect, a computer-assisted literature research was performed and manufacturers were asked to supply the author with study results. A total of 12 placebo-controlled trials with hypericum extracts were performed, mostly with positive results. Also in comparison with synthetic antidepressants (3 studies published), a similar reduction of depressive symptomatology was seen, although the comparators were not adequately dosed. No trials in severely depressed patients have been published yet. Since most studies on hypericum have methodological flaws, further studies are warranted.