1. Institute of Health & Society, Baddiley-Clark Building, Newcastle University, Newcastle upon Tyne, UK
2. Centre for Health Services Research, University of Kent, Canterbury, UK
3. Newcastle Clinical Trials Unit, Institute of Health & Society, Newcastle University, Newcastle upon Tyne, UK
4. Northumberland, Tyne and Wear NHS Foundation Trust, Newcastle upon Tyne, UK
5. Institute of Psychiatry, King’s College London, London, UK
6. Young People’s Drug and Alcohol Department, North Tyneside Council, Newcastle upon Tyne, UK