Date	Event	Description
22 August 2012	New search has been performed	Update search was performed from January 2008 to 31 December 2011 and five new studies were identified. Information on process or partnership evaluations has been included where available. Meta‐analysis was performed using studies with comparable outcomes. Summary of findings table was added. The evidence base remains weak and results are largely unchanged.
26 July 2011	Amended	Response rate exclusion criteria made more explicit. Five year assessment data for Bertelsen have been excluded as response rate was less than 60%. More detailed reasons for exclusion have been given in the characteristics of excluded studies table. Lumley 2006 reference corrected.
11 August 2010	New search has been performed	Final draft submitted for editorial approval