| Date | Event | Description |
|---|---|---|
| 12 May 2009 | New citation required but conclusions have not changed | Author list updated |
| 31 March 2009 | Amended | Two new studies added, no change to conclusions |
| 13 October 2008 | Amended | Converted to new review format. |
| 30 November 2005 | New citation required and conclusions have changed | Substantive amendment |
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