No specific funding has been awarded to this project. Dr Daniel Leightley is partly funded by the Forces in Mind Trust, a funding scheme run by the Forces in Mind Trust using an endowment awarded by the National Lottery Community Fund, and NIHR Maudsley Biomedical Research Centre. Professor Nicola Fear is partly funded by the United Kingdom’s Ministry of Defence. Professor Nicola Fear sits on the Independent Group Advising on the Release of Data at NHS Digital. Professor Nicola Fear is also a trustee of a military-related charity. Ms Alice Wickersham is in receipt of a PhD studentship funded by the National Institute for Health Research (NIHR) Biomedical Research Centre at South London and Maudsley NHS Foundation Trust and King’s College London. Dr Cerisse Gunasinghe is partly funded by the NIHR Maudsley Biomedical Research Centre. The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR, the Department of Health and Social Care, or the UK Ministry of Defence.