1 Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden; Gastroenterology Unit, Department of Gastroenterology, Dermatovenereology and Rheumatology, Karolinska University Hospital, Stockholm, Sweden.
2 Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden; Department of Paediatrics, Örebro University Hospital, Örebro, Sweden; Department of Medicine, Columbia University College of Physicians and Surgeons, New York, New York.
3 Clinical Epidemiology Division, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden; Sachs' Children and Youth Hospital, Stockholm South General Hospital, Stockholm, Sweden.