1. Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden;
2. Department of Pediatric Gastroenterology, Sachs’ Children’s Hospital, Stockholm, Sweden;
3. Clinical Epidemiology Unit, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden;
4. Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden;
5. Department of Surgery, Linköping University Hospital, Linköping, Sweden;
6. Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden;
7. Department of Internal Medicine, Södra Älvsborgs sjukhus, Borås, Sweden;
8. Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden;
9. Department of Gastroenterology, Faculty of Medicine and Health, Örebro University, Örebro, Sweden;
10. Department of Pediatrics, Örebro University Hospital, Örebro, Sweden;
11. Division of Epidemiology and Public Health, School of Medicine, University of Nottingham, Nottingham, UK;
12. Department of Medicine, Columbia University College of Physicians and Surgeons, New York, NY, USA