"Our results support the use of hypericum perforatum (St John's wort) as an alternative to the standard anti-depressant for moderate to severe depression, especially because it is well tolerated," a paper published in the British Medical Journal reported.

The scientists compared the effect of the plant extract with a commonly used depression drug, paroxetine, in patients with moderate to major depression.

The participants comprised 251 adults aged between 18 and 70 from 21 psychiatric primary care centres in Germany [Images].

"At the end of trial, half (61 out of 122) of those who took St John's Wort found their symptoms in decline, while only a third (43 out of 122) of those who took paroxetine went into remission," it said.

"For patients who didn't respond well to the initial (lower) dose, an increase in dose after two weeks was beneficial," it said.

Participants who took paroxetine suffered more side-effects, with 269 adverse effects being reported over the treatment period, while those taking St John's Wort reported 172 adverse effects. The most common in both cases was stomach disorder, the report said.