1. Department of Psychological Medicine, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, UK
2. Centre for Health Services Research, Faculty of Medicine, The University of Queensland, Brisbane, QLD, Australia
3. Institute of Epidemiology and Health Care, University College London, London, UK
4. Global Drug Survey Ltd, London, UK
5. Department of Neuropsychology and Psychopharmacology, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, Netherlands
6. South London and Maudsley NHS Foundation Trust, London, UK