Date	Event	Description
11 September 2008	Amended	Converted to new review format.
3 November 2004	New search has been performed	The search was updated in October 2004. Two new trials have been added (Weaver 2002, Raphael 2004), although the latter is published only in abstract form. The discussion section has been revised accordingly, and now includes a critical overview of some of the methodologic and statistical limitations presented by each of the published trials.