1. Institute for Sex Research , Sexual Medicine, and Forensic Psychiatry, , D-20246 Hamburg , Germany
2. University Medical Centre Hamburg-Eppendorf , Sexual Medicine, and Forensic Psychiatry, , D-20246 Hamburg , Germany
3. Project SEXUS Group , Department of Epidemiology Research, , DK-2300 Copenhagen , Denmark
4. Statens Serum Institut , Department of Epidemiology Research, , DK-2300 Copenhagen , Denmark
5. Center for Sexology Research , Department of Clinical Medicine, , DK-9000 Aalborg , Denmark
6. Aalborg University , Department of Clinical Medicine, , DK-9000 Aalborg , Denmark