Fig. 1

Data collection and respondents of the Young Helsinki Health Study cohort in the different data collection methods. *A vast majority of responses were collected via online surveys. Surveys were mailed to those without an email address and as reminders to all. All mail survey recipients could also reply online, using their personal login details provided with the mailed survey. Finally, telephone interviews were conducted among those who did not respond after reminders, and had an unclassified telephone number (n = 3266). **Based on permissions from the register data holders