Date	Event	Description
13 February 2014	New citation required but conclusions have not changed	This updated review added seven new studies to the original three. The total number of participants increased to 11,063 people. The conclusions did not change. Authorship of the review has changed in this version.
18 March 2013	New search has been performed	Searches updated to 18 March 2013.
18 March 2013	Amended	We used new search strategies, compiled by the Cochrane Consumers and Communication Review Group. There were some changes in the databases searched, due to changes in access. We updated the study design criterion to incorporate more rigorous requirements for controlled before and after studies and interrupted time series. We now use the term 'quasi‐randomised controlled trials' instead of 'controlled clinical trials'. Adverse events and source of funding were included in the data extraction. There have been minor changes to the wording of the objectives, and revision of background information. Additional information on the validation of trust scales is given in a new table. We assessed all included studies using the Cochrane Collaboration's 'Risk of bias' tool.