The herbal remedy St John's Wort effectively treats symptoms of major depression, according an analysis of previous studies published in the Cochrane Review.
Researchers said St John's Wort extracts tested in the different trials were better than placebos and as effective as standard antidepressants with fewer side effects.
The review analysed 29 studies that together included 5,489 men and women with symptoms of major depression and compared the remedy's effectiveness with placebos and standard treatments.
The researchers found that St John's Wort extracts were not only effective but that fewer people taking them dropped out of the trials due to adverse side effects.
They also noted that results were more favourable in German-speaking countries where doctors often prescribe the remedy and cautioned against using the remedy without medical advice because the extracts can affect how other drugs work.
In Germany such herbal treatments are also more controlled for content, unlike in many other markets where the quality and content of herbal products may vary considerably.
"Using a St John's Wort extract might be justified, but products on the market vary considerably, so these results only apply to the preparations tested," wrote Klaus Linde of the Centre for Complementary Medicine in Munich, Germany.
The herb works in a similar way to some prescription antidepressants by increasing the brain chemical serotonin, involved in controlling mood.