| Date | Event | Description |
|---|---|---|
| 22 September 2008 | Amended | Converted to new review format. |
| 11 April 2006 | New citation required and conclusions have changed | Substantive amendment For this first update new searches were completed in January 2006. Twelve new RCTs have been included, giving a total of 31 included trials, and 34 new excluded studies. One trial which was awaiting assessment (Wilson 1996) has been included in this update. |
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