1 National Addictions Centre, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, United Kingdom.
2 Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Victoria, Australia.
3 Institute for Social Science Research, The University of Queensland, Brisbane, Queensland, Australia.
4 South London and Maudsley NHS Trust/King's College London, London, United Kingdom.