1. Salvation Army Centre for Addiction Services and Research, Faculty of Social Sciences, University of Stirling, Stirling FK9 4LA, UK
2. NHS Lanarkshire, Bothwell G71 8BB, UK
3. School of Applied Sciences, Edinburgh Napier University, Edinburgh EH11 4BN, UK
4. School of Medicine, Molecular and Clinical Medicine, University of Dundee, Dundee DD1 4HN, UK
5. Faculty of Social Sciences, University of Stirling, Stirling FK9 4LA, UK
6. Independent Researcher, Edinburgh EH17, UK
7. School of Health and Life Sciences, Glasgow Caledonian University, Glasgow G4 0BA, UK
8. NHS Grampian, Aberdeen AB15 6RE, UK
9. School of Medicine, St. Andrews University, St. Andrews KY16 9TF, UK