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Clinical studies of St John's wort preparations have mainly focused on the efficacy of the herb in clinical depression. Several studies and meta-analyses have found it to be effective in the treatment of mild to moderate depression, with fewer side effects than many conventional antidepressants. Other studies, including a major NIH study that focused on moderate to severe depression, have shown no improvements.
Evidence for efficacy
An early meta-study indicated that extracts of Hypericum may be more efficacious than placebo for the treatment of mild to moderately severe depressive disorders.[4] This study, which covered the results from 23 smaller, earlier studies, is perhaps the most often cited by manufacturers and other supporters of St. John's wort.
This study was later updated to include further studies, for a total of 27, to form a Cochrane Review. The updated review found that Hypericum preparations were significantly superior to placebo (rate ratio 2.47; 95% confidence interval 1.69 to 3.61) and similarly effective as standard antidepressants (single preparations 1.01; 0.87 to 1.16, combinations 1.52; 0.78 to 2.94).
Another meta-analysis, with stricter inclusion criteria, found that Hypericum was more efficacious than placebo; and as efficacious as tricyclic antidepressants, with fewer adverse drug reactions. This meta-analysis showed that the response rate for St. John’s wort was significantly greater than that for placebo (73.2 versus 37.9%, respectively, relative risk 1.48 and 95% CI 1.03–1.92) and similar to that observed with tricyclic antidepressants (64 versus 66.4% for St. John’s wort and tricyclic antidepressants, respectively, relative risk 1.11 and 95% CI 0.92–1.29).
Other, more recent trials have also shown greater efficacy than placebo, and comparable efficacy to standard antidepressants with a superior adverse effect profile.
Additionally, a 2006 study involving 150 patients with minor depressive symptoms or dysthymia found that St. John's Wort has a clinically significant effect in patients with minor depression, but not those suffering from dysthymia. It was concluded that St. John's Wort can be effective in the treatment of people with minor depression with a Hamilton Depression Scale for Depression (HAM-D) score of up to 17.
[edit] Evidence against efficacy for Major Depressive Disorder
A major study funded by the NIH in the United States, found that Hypericum extract of St John's wort was ineffective in treating moderate to severe cases of major depression (Hypericum Depression Trial Study Group, 2002). This study involved 340 patients, diagnosed with Major Depressive Disorder based on DSM-IV criteria and assessed using Hamilton Depression Rating Scale (HAM-D) and Clinical Global Impression (CGI) scores. The trial was a multi-centre randomised double-blind placebo-controlled trial, comparing one preparation of St John's wort (Li 160) to the antidepressant, sertraline and to placebo. Li 160 proved no more effective than placebo in alleviating moderately severe major depression. Sertraline was also no better than placebo in this study, based on the primary outcome measure (the HAM-D).
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