We would like to thank persons formerly on the authorline of this protocol who made contributions at the early stages: Carol Joughin, Sima Pindoria (UK). Thanks also to members of the original steering group at the Systematic Reviews Training Unit, Institute of Child Health, University College London (UK), especially Stuart Logan.

Thanks also to Geraldine Macdonald (Co‐ordinating Editor, CDPLPG) for her hard work and support of this project; to Jo Abbott (former Trials Search Co‐ordinator of the Cochrane Developmental, Psychosocial and Learning Problems Group (CDPLPG)) for searches, and to anonymous statistical editors within the Cochrane and Campbell Collaborations. We are also grateful to Krystyna Kowalski (SFI Campbell, Denmark) for her patience and support over several years and to Cathy Bennett (Systematic Research Ltd, UK) for continuing assistance and attention to detail.

We would also like to thank those who helped us in obtaining potential studies for the review, including: Julie Millener (formerly of the CDPLPG editorial base), Yanina Sguassero (CDPLPG author, Argentina) and Jutta Stoffers (CDPLPG author, Germany). Thanks also to Angela Huertas‐Ceballos (CDPLPG author, UK), Toby Lasserson of the Cochrane Airways Group (UK), Danielle Ouwejan of the University of Bristol (UK) and Dr Qihua Ye (People's Republic of China), who provided assistance with translations of potential studies from Spanish, German, Dutch and Chinese, respectively.

We would like to thank numerous primary investigators who assisted us in providing clarification on aspects of methodology and data from studies cited within this review. They include Dr Michelle Beyer (USA), Dr Anil Chacko (USA), Dr Richard Conte (USA), Dr Maj Britt Drugli and Dr Sturla Fossum (Norway), Dr Chauntel Gustis (USA), Professor Nick Ialongo (USA), Dr Sue Odom (USA), Professor Lawrence Scahill (USA) and Professor Stephen Scott (UK).