[1] Univ Plymouth, Fac Hlth & Social Work, Plymouth PL4 8AA, Devon, England
[2] Ayrshire Cent Hosp, NHS Ayrshire & Arran, Irvine KA12 8SS, Scotland
[3] Univ Glasgow, Div Community Based Sci, Publ Hlth & Hlth Policy Sect, Glasgow G12 8QQ, Lanark, Scotland
[4] Heriot Watt Univ, Sch Math & Comp Sci, Edinburgh, Midlothian, Scotland
[5] Univ E Anglia, Sch Med, Norwich NR4 7TJ, Norfolk, England
[6] Greater Glasgow Primary Care NHS Trust, STEPS, Glasgow G42 8AT, Lanark, Scotland