1 Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
2 Department of Child Psychiatry, Medical University of Warsaw, Warsaw, Poland.
3 Department of Gastroenterology, Faculty of Medicine and Health, Örebro University, Örebro, Sweden.
4 Division of Surgery, Department of Clinical and Experimental Medicine, Faulty of Health Sciences, Linköping University and Department of Surgery, County Council of Östergötland, Linköping, Sweden.
5 Sachs' Children and Youth Hospital, Stockholm South General Hospital, Stockholm, Sweden.
6 Clinical Epidemiology Unit, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden.
7 Child and Adolescent Psychiatry Research Center, Stockholm, Sweden.
8 Department of Clinical Neuroscience, Karolinska Institute, Stockholm, Sweden.
9 Department of Pediatrics, Örebro University Hospital, Örebro University, Örebro, Sweden.