Stage I

Shortly after consent, the first stage implies filling in a questionnaire online (a hard copy if sent by post if wished) during about 45 - 60 minutes.

This questionnaire is about the participants' socioprofessional and family background, their consumption of alcohol, cannabis and other drugs, as well as their personality.

This stage is rewarded with a CHF 30.- voucher, which is sent shortly after the questionnaire is filled in.

Participants who filled in both questionnaires in stages 1 & 4 get another CHF 30.- voucher.

Participants are invited to fill in this questionnaire by email. In this email, they find a personal link to the online questionnaire. Those who prefer to fill in a hard copy can get it by post with a postal-paid cover. They also receive a personal access code to the questionnaire online, in case their found it more convenient.

If any problem should come out, participants can get in touch with:

• our partner GfK (c-surf@gfk.ch) for technical problems related to the online questionnaires;
• our project adminstrator (contact@c-surf.ch or 021 314 90 07) for questions related to the study or the content of the questionnaires.