Funding for this research was provided by:
University of Gothenburg
Received: 26 November 2020
Accepted: 27 May 2021
First Online: 10 June 2021
: The study was approved by the Ethics Committee at the Sahlgrenska Academy at the University of Gothenburg. Both pupils and their parents or guardians gave a written informed consent to participation and use of data for research.
: Not applicable.
: The authors declare that they have no competing interests.