| Date | Event | Description |
|---|---|---|
| 18 March 2009 | New search has been performed | The searches were updated in February 2009; no new studies were found. Risk of bias table has been completed. |
| 5 May 2008 | Amended | Converted to new review format. |
| 30 April 2007 | New search has been performed | The searches were updated in August 2006; no new studies were found. |
| 25 April 2004 | New citation required and conclusions have changed | Substantive amendment |
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