1. Cumbria, Northumberland, Tyne and Wear NHS Foundation Trust, St. Nicholas Hospital, Jubilee Road, NE3 3XT, Newcastle upon Tyne, UK
2. Centre for Health Services Studies, University of Kent, Canterbury, Kent CT2 7NF, UK
3. Institute of Health and Society, Newcastle University, Baddiley-Clark Building, NE2 4AX, Newcastle-upon-Tyne, UK
4. Addictions Department, National Addiction Centre, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, 16 de Crespigny Park, London SE5 8AF, UK