Consent

All young men at the recruitment centers in Lausanne (VD), Windisch (AG) and Mels (SG), Switzerland, were invited to participate in the C-SURF study. Those who gave their consent were invited to:

• fill in a short questionnaire on site (5-10 minutes) in French or in German;
• fill in a consent form with their personal contact details as well as those of a peer or family member. The latter are contacted by the study team only if the participant could not be reached. Participants' personal data are kept highly confidential and are at no point communicated to peers and family.

Thus, all French-speaking as well as a great part of German-speaking young men in Switzerland were invited to participate to the C-SURF study (participants in 21 of 26 swiss cantons):