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Article History

Received: 31 October 2017

Accepted: 18 June 2018

First Online: 28 June 2018

Compliance with ethical standards

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: The authors declare that they have no conflict of interest.

: All participants were given written information about the study objectives and modalities (points of assessment, length of questionnaires), data preparation and pseudonymised data storage, the expected amount of commitment, the voluntary nature of participation and their right to withdraw at any time. Furthermore, participants were informed verbally about the study purpose and procedures and were given the chance to ask questions. All participants provided written informed consent. All countries assure that data processing and storage is done in line with European and national data protection rules. Where necessary, the study procedures were approved by an ethical committee. In Norway, the Norwegian Center for Research Data approved the study (44003). In Germany, the Institutional Review Board of the Medical Faculty by the University of Heidelberg approved the study (S-611/2015). In Sweden, the study was approved by the Regional Ethical Review Board in Umeå (2015/357-31Ö). In France, the project needed to fullfil the obligations of the CNIL (Commission Nationale Informatique et Libertés), no specific ethical approval was necessary.