Funding for this research was provided by:
The Nordea Denmark Foundation (02-2011-0122)
Research Council for Health and Illness (271-06-2045 / 09-061516)
Text and Data Mining valid from 2018-03-16
Received: 3 August 2017
Accepted: 8 March 2018
First Online: 16 March 2018
Ethics approval and consent to participate
: There is no formal agency for ethical approval of school surveys in Denmark. Therefore we asked the school leader, the board of pupils, and the board of parents who serves as the parents’ representatives in each of the participating schools for assessment and approval of the study. All procedures performed in studies involving human participants were in accordance with the national ethical guidelines and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.The pupils received oral and written information about the study and that participation was voluntary and anonymous.
: Not applicable.
: The authors declare that they have no competing interests.
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