The review, by scientists from the Centre for Complementary Medicine at the Technical University of Munich and the University Medical Center Freiburg, also supports earlier research that showed the plant extract is effective against mild to moderate depressive disorders.
"Overall, we found that the St. John's wort extracts tested in the trials were superior to placebos and as effective as standard antidepressants, with fewer side effects," said lead researcher, Klaus Linde.
Extracts of the plant Hypericum perforatum, commonly known as St. John's wort, have already been shown to help in patients with minor depression but in patients with more severe depression, the efficacy has been disputed.
The new review pulled together 29 trials involving 5,489 patients with symptoms of major depression. Eighteen trials included a placebo and 17 involved comparisons with synthetic standard antidepressants. All the trials used the Hamilton Rating Scale for Depression to assess the severity of depression.
In the nine largest trials of the 18 placebo-controlled trials, the researchers report that hypericum extracts were 28 per cent more effective, while the response rate was 87 per cent higher in the patients receiving the St John’s wort extract in the nine smaller trials.
When compared to the standard antidepressants, and selective serotonin reuptake inhibitors (SSRIs), the researchers found no difference in efficacy. However, the drop out rate by patients receiving St John’s wort was 76 per cent lower than amongst patients receiving tri- or tetracyclic antidepressants, and 47 per cent lower than amongst patients receiving SSRIs.
“The available evidence suggests that the hypericum extracts tested in the included trials a) are superior to placebo in patients with major depression; b) are similarly effective as standard antidepressants; c) and have fewer side effects than standard antidepressants,” wrote the researchers.
Muddying the waters
Linde and his co-workers report that the overall picture is complicated by more favourable results being report in trials conducted in German speaking countries. The herbal has a long tradition of use in these countries, they said, and it is often prescribed by doctors.
Despite the positive results, the researchers caution against generalisations about the plant's efficacy. "Using a St. Johns wort extract might be justified, but products on the market vary considerably, so these results only apply to the preparations tested," said Linde.
The little yellow flower and health claims
Earlier this summer, UK botanicals manufacturer Bioforce was granted the right to make a claim that St John’s wort can help "low mood" and "mild anxiety”, after winning a Traditional Herbal Medicinal Products Directive (THMPD) registration. But the claim cannot claim to treat depression.
The UK manufacturer first sought to make a mood-based claim for a St John's Wort product in 1995, but was rebuffed by the UK Medicines and Healthcare products Regulatory Agency (MHRA) for failing to meet the body's "standards of evidence".
Source: Cochrane Systematic Review2008, Issue 4. Art. No.: CD000448. doi: 10.1002/14651858.CD000448.pub3.“St John's wort for major depression”Authors: K. Linde, M.M. Berner, L. Kriston