[1] Univ Bath, Dept Psychol, Bath BA2 7AY, Avon, England
[2] UCL, Res Dept Primary Care & Populat Hlth, London NW3 2PF, England
[3] UCL, Ctr Behav Change, Res Dept Clin Educ & Hlth Psychol, 1-19 Torrington Pl, London WC1E 7HB, England
[4] Univ Bristol, Dept Expt Psychol, Priory Rd, Clifton BS8 1TU, England
[5] Whittington Hlth, Magdala Ave, London N19 5NF, England
[6] Univ Southampton, Fac Hlth Sci, Southampton SO17 1BJ, Hants, England
[7] Univ Oxford, Nuffield Dept Primary Care Hlth Sci, Oxford OX2 6GG, England
[8] Univ Southampton, Dept Psychol, Bldg 44 Highfield Campus, Southampton SO17 1BJ, Hants, England
[9] London Sch Hyg & Trop Med, 15-17 Tavistock Pl, London WC1H 9SH, England