1. Search history.

Years (from/to)	Detail
All years to January 2002	References identified: 438 titles and abstracts Possibly relevant: 107 studies for inclusion. Full text versions of these papers were obtained & assessed independently by NM and AB. Where a query arose about a study's fulfilment of the inclusion criteria, the authors were contacted for further confirmation. If the trial had presented both child and adult data together, authors were asked if they could provide the data for children separately. No further information was provided by study authors. N included: Eight. All study authors contacted to clarify information. N excluded: 99 papers (reasons for exclusion detailed in 'Characteristics of Excluded Studies' . Nine out of the 107 studies were published in a foreign language (one in French, one in Polish, three in Spanish, two in Italian, one in German, and one in Dutch). No study was excluded on the basis of language of publication. Translations have been obtained for all studies. Two non‐English language papers met the inclusion criteria for this review and were included (Vazquez 1984; Zimmermann 1984).
January 2002 to February 2005	References identified: 32 titles and abstracts. Possibly relevant: Six (Dutt 1990; Krasnowska 1994; Krasnowska 2004; Li 2003; Miraglia 1983; Pauwels 1995). N included: 0 N excluded: six
February 2005 to February 2006	References identified: 26 Possibly relevant: 0
February 2006 to February 2007	References identified: 20 Possibly relevant: 0
February 2007 to February 2008	References identified: 14 Possibly relevant: 0
February 2008 to February 2009	References identified: 10 Possibly relevant:0