1 National Addiction Centre, Institute of Psychiatry, Psychology and Neuroscience, King's College, London, United Kingdom. Electronic address: polly.radcliffe@kcl.ac.uk.
2 School of Health in Social Science, University of Edinburgh, United Kingdom.
3 Department of Sociology and Social Anthropology, Dalhousie University, Canada.
4 NMAHP Research Unit, University of Stirling, United Kingdom.