Mental health in UK Biobank: development, implementation and results from an online questionnaire completed by 157 366 participants — RETRACTED. Issue 4 (July 2019) - Davis, Katrina A. S.; Coleman, Jonathan R. I.; Adams, Mark; Allen, Naomi; Breen, Gerome; Cullen, Breda; Dickens, Chris; Fox, Elaine; Graham, Nick; Holliday, Jo; Howard, Louise M.; John, Ann; et al.