1. Centre for Epidemiology, Division of Population Health, Health Services Research and Primary Care, University of Manchester, Manchester, M13 9PL, UK;
2. Centre of Biostatistics, Division of Population Health, Health Services Research and Primary Care, University of Manchester, Manchester, M13 9PL, UK;
3. Centre for Mental Health and Safety, Division of Psychology and Mental Health, University of Manchester, Manchester, M13 9PL, UK