Footnotes

• Contributors RJE assisted in designing the study, reviewed identified manuscripts and selected those matching inclusion criteria, drafted and critically reviewed the manuscript, and approved the final version of the manuscript. SB and KMG

  assisted in designing the study, reviewed identified manuscripts and selected those matching inclusion criteria, edited and critically reviewed the manuscript, and approved the final version of the manuscript.

  GAD assisted in designing the study, reviewed identified manuscripts and selected those matching inclusion criteria, edited and critically reviewed the manuscript, and approved the final version of the manuscript.

  AH performed the literature searches, drafted tables and methodological statements, performed statistical analyses, edited and critically reviewed the manuscript, and approved the final version of the manuscript.

  JJL assisted in designing the study, reviewed identified manuscripts and selected those matching inclusion criteria, edited and critically reviewed the manuscript, and approved the final version of the manuscript.

  WPM assisted in designing the study, reviewed identified manuscripts and selected those matching inclusion criteria, edited and critically reviewed the manuscript, and approved the final version of the manuscript.

  MP assisted in designing the study, reviewed identified manuscripts and selected those matching inclusion criteria, edited and critically reviewed the manuscript, and approved the final version of the manuscript. J

  S assisted in designing the study, reviewed identified manuscripts and selected those matching inclusion criteria, edited and critically reviewed the manuscript, and approved the final version of the manuscript. KJ

  S assisted with executing searches, coordinated risk of bias and level of evidence assessments, and coordinated content of the data extraction tables. She edited and critically reviewed and approved the final version of the manuscript. PM assisted in the design of the study. critically reviewed and approved the final manuscript.

• Funding SB receives research funding through NIH-NINDS (3R15NS081691-01S1 and 1R15NS081691-01), National Collegiate Athletic Association and USA Medical Research Acquisition Activity (W81XWH-14-2-0151: 14132004). He also is reimbursed for travel expenses for lectures and scientific meetings. GAD is an honorary member of the Australian Football League Concussion Working Group, and has attended meetings organised by sporting organisations including the National Football League (USA), National Rugby League (Australia) and FIFA (Switzerland); however, he has not received any payment, research funding or other monies from these groups other than for travel costs. RJE is a consultant to the National Hockey League, Major League Soccer, US Soccer Federation and Princeton University. He receives financial remuneration for these consulting relationships. He has a clinical practice in sport neuropsychology and serves as an expert (neuropsychology, sport neuropsychology) in medico-legal cases involving traumatic brain injury. RJE at times receives honoraria and reimbursement of expenses to attend professional meetings. KMG is the Founding Director of the Matthew Gfeller Sport-Related TBI Research Center at the University of North Carolina (USA). He is a member of the National Collegiate Athletic Association’s Concussion Committee and the US Soccer Federation (unpaid consultant for both). KMG at times receives honoraria and reimbursement of expenses to speak at professional meetings. AH has nothing to disclose. PM is a co-investigator, collaborator or consultant on grants relating to mild TBI funded by several governmental organisations. He is directly employed by the National Health and Medical Research Council of Australia and is based at The Florey Institute of Neuroscience and Mental Health. He is Co-Chair of the Australian Centre for Research into Sports Injury and its Prevention (ACRISP), which is one of the International University Research Centres for Prevention of Injury and Protection of Athlete Health supported by the International Olympic Committee (IOC). He is co-chair of the International Concussion in Sport Group. He has a clinical and consulting practice in general and sports neurology. He receives book royalties from McGraw-Hill and was employed in an editorial capacity by the British Medical Journal Publishing Group from 2001 to 2008. He has been reimbursed by the government, professional scientific bodies and sporting bodies for travel costs related to presenting research on mild TBI and sport-related concussion at meetings, scientific conferences and symposiums. He received consultancy fees in 2010 from Axon Sports (USA) for the development of educational material (which was not renewed) and has received research funding since 2001 from Cogstate Inc. He has not received any research funding, salary or other monies from the Australian Football League, FIFA or the National Football League. The Australian Football League funds research at the Florey Institute under a legal memorandum, and PM does not receive any money from this industry-funded research. PM is a cofounder and shareholder in two biomedical companies (involved in eHealth and compression garment technologies) but does not hold any individual shares in any company related to concussion or brain injury assessment or technology. He did not receive any form of financial support directly related to this manuscript. WPM receives royalties from (1) ABC-Clio publishing for the sale of his books Kids, Sports, and Concussion: A Guide for Coaches and Parents, and Concussions; (2) Springer International for the book Head and Neck Injuries in Young Athlete; and (3) Wolters Kluwer for working as an author for UpToDate. His research is funded, in part, by philanthropic support from the National Hockey League Alumni Association through the Corey C. Griffin Pro-Am Tournament and by a grant from the Football Players Health Study at Harvard University, which is funded by the NFL Players Association. JJL receives grants/research support from National Institutes of Health, The Ralph C. Wilson Foundation, Program for Understanding Childhood Concussion and Stroke, The Robert Rich Family Foundation, and The Buffalo Sabres Foundation. MP is a medical consultant for Major League Soccer and received financial remuneration for this relationship. She has served as a medical expert on medico-legal cases involving sports medicine and traumatic brain injury and received financial remuneration for these. MP also serves on several committees including the US Lacrosse Sports Science and Safety Committee, US Soccer Medical Committee, and the NFL Head, Neck and Spine Committee, and has received reimbursement of expenses to attend these as well as other professional meetings. KJS has received speaking honoraria for presentations at scientific meetings. She is a physiotherapy consultant at Evidence Sport and Spinal Therapy. JS holds an academic appointment in the School of Physiotherapy at the University of Otago (Dunedin, New Zealand). He occasionally receives reimbursement of expenses to attend professional meetings.

• Provenance and peer review Not commissioned; externally peer reviewed.

• Author note To the editor-in-chief of BJSM, Dr Karim Khan, the present paper has been commissioned by Professor Lars Engebretsen and is intended to be part of the BJSM IPHP theme issue on concussion in March 2017. This paper is internally reviewed by the expert group represented at the Berlin Consensus meeting on Concussion in Sport in October 2016.