Background: Extracts of the plant Hypericum perforatum L. (popularly called St. John's wort) have been used in folk medicine for a long time for a range of indications including depressive disorders.
Objectives: To investigate whether extracts of hypericum are more effective than placebo and as effective as standard antidepressants in the treatment of depressive disorders in adults; and whether they have have less adverse effects than standard antidepressant drugs.
Search strategy: Trials were searched in computerized databases (Cochrane Collaboration Depression, Anxiety & Neurosis Group Clinical Trials Registers; PubMed); by checking bibliographies of pertinent articles; and by contacting manufacturers and researchers.
Selection criteria: Trials were included if they: (1) were randomized and double-blind; (2) included patients with depressive disorders; (3) compared extracts of St. John's wort with placebo or standard antidepressants; and (4) included clinical outcomes such as scales assessing depressive symptoms.
Data collection and analysis: Information on patients, interventions, outcomes and results was extracted by at least two independent reviewers using a standard form. The main outcome measure for comparing the effectiveness of hypericum with placebo and standard antidepressants was the responder rate ratio (responder rate in treatment group/responder rate in control group). The main outcome measure for adverse effects was the number of patients dropping out for adverse effects.
Main results: A total of 37 trials, including 26 comparisons with placebo and 14 comparisons with synthetic standard antidepressants, met the inclusion criteria. Results of placebo-controlled trials showed marked heterogeneity. In trials restricted to patients with major depression, the combined response rate ratio (RR) for hypericum extracts compared with placebo from six larger trials was 1.15 (95% confidence interval (CI), 1.02-1.29) and from six smaller trials was 2.06 (95% CI, 1.65 to 2.59). In trials not restricted to patients with major depression, the RR from six larger trials was 1.71 (95% CI, 1.40-2.09) and from five smaller trials was 6.13 (95% CI, 3.63 to 10.38). Trials comparing hypericum extracts and standard antidepressants were statistically homogeneous. Compared with selective serotonin reuptake inhibitors (SSRIs) and tri- or tetracyclic antidepressants, respectively, RRs were 0.98 (95% CI, 0.85-1.12; six trials) and 1.03 (95% CI, 0.93-1.14; seven trials). Patients given hypericum extracts dropped out of trials due to adverse effects less frequently than those given older antidepressants (Odds ratio (OR) 0.25; 95% CI, 0.14-0.45); such comparisons were in the same direction, but not statistically significantly different, between hypericum extracts and SSRIs (OR 0.60, 95% CI, 0.31-1.15).
Authors' conclusions: Current evidence regarding hypericum extracts is inconsistent and confusing. In patients who meet criteria for major depression, several recent placebo-controlled trials suggest that the tested hypericum extracts have minimal beneficial effects while other trials suggest that hypericum and standard antidepressants have similar beneficial effects. As the preparations available on the market might vary considerably in their pharmaceutical quality, the results of this review apply only to the products tested in the included studies.