| Date | Event | Description |
|---|---|---|
| 28 January 2013 | New search has been performed | Updated |
| 28 January 2013 | New citation required but conclusions have not changed | The updated search on 9 January 2013 identified no new studies. The conclusion remains unchanged. |
| 8 July 2009 | New search has been performed | The search was updated on 25th June 2009, no new studies were identified. The conclusions remain unchanged. |
| 8 September 2008 | Amended | Converted to new review format. |
| 14 May 2007 | New citation required and conclusions have changed | Substantive amendment |
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