1. Department of Clinical Science and Education, Södersjukhuset, Karolinska Institutet, Stockholm, Sweden;
2. Clinical Epidemiology Unit, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden;
3. Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden;
4. Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden;
5. Center for Digestive Disease, Div. of Coloproctology, Karolinska University Hospital, Stockholm, Sweden;
6. Division of Surgery, Department of Clinical and Experimental Medicine, Faulty of Health Sciences, Linköping, Sweden;
7. University and Department of Surgery, County Council of Östergötland Linköping, Linköping, Sweden;
8. Gastroenterology Unit, Crohn’s and Colitis Center, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA;
9. Department Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden;
10. Department of Gastroenterology, Faculty of Medicine and Health, Örebro University, Örebro, Sweden;
11. Department of Pediatrics, Örebro University Hospital, Örebro University, Örebro, Sweden;
12. Division of Epidemiology and Public Health, School of Medicine, University of Nottingham, Nottingham, UK;
13. Department of Medicine, Columbia University College of Physicians and Surgeons, New York, NY, USA;
14. Department of pediatric gastroenterology and nutrition, Sachs' Children and Youth Hospital, Stockholm, Sweden