Date	Event	Description
11 August 2011	New search has been performed	New literature search run. No new eligible studies identified. Minor copy edits made.
29 September 2009	New citation required but conclusions have not changed	New authorship of the review.
27 August 2009	New search has been performed	New search conducted, added new included study (Taylor 2004), amendments made to Plain Language Summary, reformatted Results and Discussion and added 'Risk of bias' and 'Summary of findings' table. Conclusions unchanged.
21 July 2008	Amended	Converted to new review format.
7 January 2005	New search has been performed	New studies found and included or excluded: 8 January 2005
8 January 2003	New search has been performed	New studies sought but none found: 8 January 2003
18 June 2001	New citation required and conclusions have changed	Substantive amendment