Received: 24 July 2019
Revised: 30 November 2020
Accepted: 12 December 2020
First Online: 23 January 2021
Compliance with Ethical Standards
: The authors declare that they have no conflict of interest.
: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional research committee (the board of the Katholieke Universiteit Leuven + OT 98/12 ZKA 2922) and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. This study is conducted in full compliance with pertinent international treaties, national laws, regulations and codes concerning research involving minors (adolescents), as well as privacy. The study protocol meets since the beginning in 1999 the requirements of the codes of conduct of pertinent professional associations, in particular of national and international psychological and behavioral associations. Given that neither interventions nor invasive actions are part of this study, the board of the Katholieke Universiteit Leuven approved this study and conforming the Belgian law no further approval was needed. The Belgian law on research with human subjects stipulates that a scientific research project is subject to formal ethical approval by a Medical-Ethical Committee if it is explicitly relevant to the medical science and experiments are used (Art. 1). In this project no medications or experiments are involved.