Large-scale observational studies of hypericum extracts in patients with depressive disorders-a systematic review

We present a systematic review of observational studies of hypericum extracts in the treatment of depressive disorders. We included non-randomized studies with at least 100 patients suffering from depressive disorders treated with hypericum mono-preparations for at least 4 weeks, which reported clinical outcomes. Potentially relevant studies were identified through searches in electronic databases (Medline, PubMed), contacts with manufacturers, and handsearching of proceedings of phytomedicine congresses. Information on patients, interventions, methods and results were extracted by two reviewers. Sixteen studies including a total of 34,804 (range 101-11,296) patients met the inclusion criteria. Most studies investigated short-term effects (4-6 weeks) in patients with mild to moderate depression. Response rates (according to physician assessment) varied between 65% and 100%, the proportion of patients dropping out due to side effects varied between 0.0% and 2.8%. Two studies investigated long-term effects (52 weeks). Reponse rates were 60% and 69%, respectively, and the proportions of patients dropping out due to side effects were 3.4% and 5.7%, respectively. Serious side effects or interactions were not reported in any study. The quality of reporting was insufficient in the majority of publications. The available studies show that hypericum extracts are well tolerated and seem to be effective in routine treatment of mild to moderate depressive disorders.