1. Division on Substance Use Disorders, New York State Psychiatric Institute & Department of Psychiatry, Columbia University Irving Medical Center, New York, New York, USA
2. National Addiction Centre, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, London, UK
3. Centre for Social Research in Health, University of New South Wales, Sydney, Australia
4. South London and Maudsley NHS Foundation Trust, Camberwell, London, UK