| Date | Event | Description |
|---|---|---|
| 4 August 2010 | Amended | Contact details updated. |
| 11 November 2009 | Amended | Plain language summary revised |
| 23 February 2009 | New search has been performed | New search carried out and two new included studies added. |
| 23 April 2008 | Amended | Converted to new review format. |
| 24 May 2006 | New citation required and conclusions have changed | Substantive amendment |
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