| Date | Event | Description |
|---|---|---|
| 12 October 2018 | New search has been performed | The review has been updated. |
| 12 October 2018 | New citation required but conclusions have not changed | The title of the review has been changed. Conclusions not changed. This update includes 12 new studies not included in the original 2010 review. |
| 12 May 2010 | Feedback has been incorporated | In response to comments from a reader (reproduced in the 'Feedback' section of this review), we have made changes to the review in the 'Background', 'Discussion', the 'Conclusions', 'Abstract' and 'Plain Language Summary'. |
| 14 April 2010 | Amended | Data on some ongoing studies has been added |
| 14 July 2008 | Amended | Converted to new review format. |
| 14 March 2008 | Amended | New author team produced revised and updated protocol |
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