Appendix 1—table 4. Qualifications to years of schooling conversion table.

Educational or professional qualifications were converted to years of schooling following Okbay et al. (2016).

Qualifications (UKB data field 6138)	Years of schooling
College or University degree	20
NVQ or HND or HNC or equivalent	19
Other professional qualifications eg: nursing, teaching	15
A levels/AS levels or equivalent	13
O levels/GCSEs or equivalent	10
CSEs or equivalent	10
None of the above	7