University College London - Department of Epidemiology and Public Health, University College London - Department of Epidemiology and Public Health, University of Liverpool - Department of Public Health, Policy and Systems, University College London - Department of Epidemiology and Public Health, Imperial College London - Ageing Epidemiology Research Unit (AGE), University College London - Department of Epidemiology and Public Health, University College London - Department of Epidemiology and Public Health, University College London - Division of Psychiatry, University of Liverpool - Department of Public Health, Policy and Systems and University College London - Department of Epidemiology and Public Health