1. Pediatric Oncology/Hematology University Children's Hospital Basel Basel Switzerland
2. Institute of Social and Preventive Medicine University of Bern Bern Switzerland
3. Center for Psychiatric Rehabilitation University Hospital for Mental Health Bern Switzerland
4. University Hospital of Psychiatry and PsychotherapyUniversity of Bern Bern Switzerland
5. Epidemiology, Biostatistics, and Prevention Institute University of Zurich Zurich Switzerland
6. Molecular Genetics Section Department of Pediatrics University of Groningen Groningen the Netherlands
7. Oslo Centre for Biostatistics and Epidemiology Oslo University Hospital Oslo Norway