1 School of Biomedical Engineering and Imaging Sciences, King's College London, London, UK.
2 Population Health Sciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK.
3 Department of Population Health, Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, UK.
4 Department of Women and Children's Health, Faculty of Life Sciences and Medicine, School of Life Course Sciences, King's College London, London, UK; Children's Neurosciences, Evelina London Children's Hospital, St Thomas' Hospital, King's Health Partners, Academic Health Science Centre, London, UK.
5 Department of Twin Research and Genetic Epidemiology, King's College London, London, UK; Department of Endocrinology, Guy's and St Thomas' NHS Foundation trust, London, UK. Electronic address: emma.duncan@kcl.ac.uk.