Reason for withdrawal from publication
The original authors of this review are unable to update it. The Cochrane Pain, Palliative and Supportive Care Review Group (PaPaS) is seeking new authors to update and split the review into two separate reviews on young children (< 12 years) and adolescents (12-17 years). If you are interested, please contact the Managing Editor of PaPaS (contact details provided under 'Contact Person').
At July 2014, this review has been withdrawn. This review is out of date although it is correct as of the date of publication. The latest version is available in the ‘Other versions’ tab on The Cochrane Library, and may still be useful to readers.