[1] Univ Aberdeen, Inst Appl Hlth Sci, Hlth Psychol Grp, Foresterhill, Aberdeen AB25 2ZD, Scotland
[2] Natl Inst Publ Hlth & Environm, Ctr Infect Dis Epidemiol & Surveillance, POB 1, NL-3720 BA Bilthoven, Netherlands
[3] Univ Utrecht, Interdisciplinary Social Sci, POB 80140, NL-3508 TC Utrecht, Netherlands
[4] UNSW Sydney, Ctr Social Res Hlth, John Goodsell Bldg, Sydney, NSW 2052, Australia
[5] Inst Prevent & Social Res IPSR, Minrebroederstr 7a, NL-3512 GS Utrecht, Netherlands
[6] STI Aids Netherlands, Condensatorweg 54, NL-1014 AX Amsterdam, Netherlands