St John’s Wort. The first draft of this page confirmed its effectiveness in mild to moderate depression but expressed caution because the active ingredient in commercial preparations varied so widely that many did not provide the required level of active ingredient hypericin (900 micrograms).
We knew that the way the drug worked may interfere with the action of other drugs and advised that as testing against such drugs had not taken place it should not be taken if any other drug was a necessity. No studies that have been carried out covered a period longer than 8 weeks so there is also no long term safety information.
Recently it was noted that persons on drugs to ensure survival of their transplanted kidneys, heart etc. were found to have significantly reduced  action of those drugs by taking St Johns Wort. Once this information became available specialists looked at potential interaction with other drugs and the danger became even clearer.
If you are taking any medication including the oral contraceptive pill DO NOT USE ST JOHNS WORT. For up to date information ask your personal medical adviser, your GP.

A study, published in 2005, showed that in the treatment of moderate to severe major depression, hypericum extract WS 5570 is at least as effective as paroxetine and is better tolerated. http://bmj.bmjjournals.com/cgi/content/full/330/7490/503

A study in Germany of 324 patients with mild to moderate depression compared St John's wort to the tricyclic antidepressant imipramine over a 6 week period. St John's wort was significantly better at reducing anxiety and was more pleasant to take. 3% withdraw from St John's wort because of intolerable side effects compared to 16% on imipramine.