Date	Event	Description
15 November 2016	New citation required but conclusions have not changed	The searches identified no new studies for inclusion. Unless new evidence emerges, we will no longer update this review.
1 November 2016	New search has been performed	We updated this review in October 2016.
20 September 2010	Amended	We updated contact details.
11 February 2009	New citation required but conclusions have not changed	We updated the review in Apirl 2008.
31 August 2008	New search has been performed	We updated searches on 21 April 2008. We found no new studies. We amended the review. We added risk of bias tables and 2 new figures. We moved search strategies to appendices.
29 April 2008	Amended	We converted the review to new review format.
23 August 2005	New citation required and conclusions have changed	We made substantive amendments.