1. Center for Alcohol and Drug Research, Stavanger University Hospital, Stavanger, Norway
2. Department of Social Studies, University of Stavanger, Stavanger, Norway
3. The Norwegian Centre for Movement Disorders, Stavanger University Hospital, Stavanger, Norway
4. Department of Research, Section of Biostatistics, Stavanger University Hospital, Stavanger, Norway
5. Faculty of Life Sciences and Medicine, King’s College London, London, UK
6. Department of Psychosocial Science, Faculty of Psychology, University of Bergen, Bergen, Norway