Lifelines variables are organized per theme in 10 main sections and ~200 subsections.
The 10 sections are:

1. Demographics
2. Diseases & Symptoms
3. Elderly
4. Family health
5. Lifestyle & environment
6. Medical treatment
7. Mental health
8. Nutrition
9. Physical state
10. Reproduction & development
11. Wellbeing & subjective health

Note that some subsections could fall under more than one section (i.e., “alcohol use” could be seen as a subsection of “lifestyle” or of “nutrition”, and “mental illness” could fall under “diseases & symptoms” or “mental health”). Similarly, individual variables may fit in more than one subsection. Lifelines always asigns a primary section and subsection to a variable, but may asign a secondary section and/or subsection to facilitate the findability of the variable in the online data catalogue.