Karolinska Institutet, University of Oslo, Karolinska Institutet, Aalborg University - Center for Molecular Prediction of Inflammatory Bowel Disease (PREDICT), Aalborg University, Aarhus University - Aarhus University Hospital, Karolinska Institutet - Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, University of Stavanger - Stavanger University Hospital, University of Oslo - Clinical Effectiveness Research Group, Norwegian Institute of Public Health, University of Oslo - Clinical Effectiveness Group and Karolinska Institutet