1. National Public Health Institute, Department of Mental Health and Alcohol Research, FI-00300, Helsinki, Finland
2. Finnair Health Services, HEL-IH/67, FI-01053 Finnair, Finland
3. Helsinki University Central Hospital, Department of Psychiatry, P.O.Box 442, FI-00029 HUS, Finland
4. University of Helsinki, Department of Psychiatry, P.O. Box 22, FI-00014 University of Helsinki, Finland