Text and Data Mining valid from 2019-05-10
Received: 29 September 2018
Accepted: 30 April 2019
First Online: 10 May 2019
Ethics approval and consent to participate
: The Portuguese 2010 HBSC study was approved by the Portuguese Ministry of Education, by the national ethics committee and the Portuguese National Data Protection System. Informed parental consent was collected from all participating schools.
: Not applicable.
: The authors declare that they have no competing interests.