1. Centre for Sexual and Reproductive Health Research; Department of Social and Environmental Health Research; London School of Hygiene and Tropical Medicine; London UK
2. MRC/CSO Social and Public Health Sciences Unit; University of Glasgow; Glasgow UK
3. Centre for Sexual Health and HIV Research; Research Department of Infection & Population Health; University College London; London UK
4. Centre for Sexual Health Research; Department of Psychology; University of Southampton; Southampton UK
5. Department of Gynaecology; Nottingham University Hospitals NHS Trust; Nottingham UK
6. Department of Psychiatry; University of Oxford; Oxford UK