Funding for this research was provided by:
Norges Forskningsråd (221047/F40)
Gjensidige Foundation (1042294)
Text and Data Mining valid from 2018-08-15
Received: 2 February 2018
Accepted: 25 July 2018
First Online: 15 August 2018
Ethics approval and consent to participate
: The South-East Regional Committee for Medical Research Ethics approved the study protocol (reference number 2013/1893). We obtained written informed consent from each child’s parents or legal guardian and from the responsible school authorities prior to all testing.
: Not applicable
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.