Date	Event	Description
15 June 2011	New search has been performed	New RCT's added this update, conclusions remain the same as previous version.
26 January 2009	New citation required and conclusions have changed	This version is the third update of the review, first published in 2001 issue 3
15 July 2008	New citation required but conclusions have not changed	Substantive amendment
15 July 2008	New search has been performed	Converted to new review format.