2.3. Ethics Approval and Informed Consent
The study protocol and related documentation were assessed and approved/expert opinions were provided (in accordance with national legislation) by competent ethics committees in each of the six countries during 2019. All participants were engaged in the study on a voluntary basis in accordance with the Declaration of Helsinki [All participants were provided with a plain-language statement describing the general purpose of the study. They were informed about the voluntary nature of their participation and their right to withdraw from the study at any time without having to provide a reason and without any adverse consequences. Information letters and informed consent forms were handed over to AYCs, one set for themselves and, when required by legislation, one set for their parents or legal guardians, to be returned later on. Written self-consent was obtained from participant AYCs and, when required by legislation, also from their parents or legal guardians. In Sweden and Switzerland, parental consent is not a legal requirement for young people aged 15–17 years. For 14-year-olds (see Data were processed in compliance with both national laws on data protection and the EU General Data Protection Regulation (GDPR) 2016/679 to guarantee the respondents’ confidentiality and privacy.The amendments introduced due to the COVID-19 pandemic received formal ethical approvals and/or detailed opinions (as appropriate according to national legislation) from the previously consulted ethics review boards in all six countries. They were informed that, due to the COVID-19 situation, it was necessary to adapt the methodological approach by replacing all personal meetings (group sessions) of the intervention with online meetings (see For more details, see the Institutional Review Board Statement at the end of the article.Ethics issues, especially those concerning the implementation of the intervention during the pandemic, were also carefully monitored by the project’s external International Advisory and Ethics Board (IAEB) until the project end.