| Date | Event | Description |
|---|---|---|
| 11 November 2009 | Feedback has been incorporated | Minor revision following peer review |
| 24 April 2009 | New citation required but conclusions have not changed | slight amendment |
| 7 January 2009 | New citation required but conclusions have not changed | Conclusion similar to previous version of this review. |
| 6 October 2008 | New search has been performed | Two new trials were added in this update |
| 15 May 2008 | Amended | Converted to new review format |
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