1. Department of Psychological Medicine, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, London, UK
2. Centre for Health Services Research, Faculty of Medicine, The University of Queensland, Brisbane, QLD, Australia
3. South London and Maudsley NHS Foundation Trust, London, UK
4. Belfast Health and Social Care Trust, Belfast, UK
5. Institute of Pharmaceutical Science, Faculty of Life Sciences and Medicine, King’s College London, London, UK
6. National Programme of Substance Abuse Deaths, Population Health Research Institute, St George’s, University of London, London, UK
7. Institute of Epidemiology and Health Care, University College London, London, UK
8. Global Drug Survey, London, UK