Young participants (13-17y) participating in baseline assessment 1A filled in a digital questionnaire at the location of 1A Visit 1 (n = ~3,900). The 1A Youth Questionnaire is procedurally equivalent to the 2A Youth Questionnaire.

The 1A Youth Questionnaire contained the following sections and subsections:

• Education
• Family composition
• Household composition
• Personal data
• Employment status

• Acne
• Allergies
• Cold/Flu
• Digestive symptoms
• Ear conditions
• Eye conditions
• Fatigue (general)
• Insomnia
• Kidney & bladder diseases
• Musculoskeletal symptoms
• Neurological disorders
• Respiratory problems (ELON)
• Respiratory problems (general)
• Skin conditions

• Alcohol use
• Drug use
• Electronic device use
• Hobbies & activities
• Home environment (general)
• Physical activity (sports)
• Smoking & tobacco use

• Medication

• Familial bonds
• Youth Self Report (YSR)

• Diet (general)
• FFQ

• Contraception
• Menstruation
• Physical development

• Subjective health (general)