== Clarifications Requested == 

 In the "Clinical evidence", the article states "Several studies and meta-analyses have found it to be effective in the treatment of mild to moderate depression, with fewer side effects than many conventional antidepressants. Other studies, including a major NIH study that focused on moderate to severe depression, have shown no improvements." 

 Did the NIH study conclude that St John's wort preparations were not even mildly effective for moderate to severe depression, with "no improvements" at all? Or did the study recognize some effectiveness even in more severe cases of depression, but concluded that conventional antidepressants were more effective treatment for moderate to sever depression?