| Date | Event | Description |
|---|---|---|
| 2 March 2011 | New citation required but conclusions have not changed | Authorship change and new studies added but conclusions not changed |
| 7 August 2010 | New search has been performed | Converted to new review format. |
| 27 July 2010 | New search has been performed | Substantial update: results of 2010 search added, six studies added to Characteristics of excluded studies table. |
| 14 April 2010 | Amended | Contact details updated. |
| 5 August 2009 | Amended | Contact details updated. |
| 25 April 2008 | Amended | Converted to new review format. |
| 3 July 2004 | New citation required and conclusions have changed | Substantive amendment |
| 18 September 2003 | New search has been performed | Search strategy was run again, no new studies were found for inclusion. |
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