Background: Most people who survive a disaster respond with psychological reactions, but only a minority suffer from lasting psychological problems. Despite evidence of the significance of specific exposures for impaired psychological health after disaster, the relative importance of single exposures remains unclarified. With regard to predisaster factors, the relevance of prior life events is not definite. As for postdisaster factors that influence health, this study of tourist survivors of the Indian Ocean tsunami of 2004 brought about a unique opportunity for studying a population which was spared most of the secondary disruption otherwise common to natural disasters. It also enabled the investigation of the impact of disaster experience on other groups than the most extremely exposed, and the highlighting of the issue of recovery, with special emphasis on intervention in the form of support. Disaster research is still evolving concerning which survivors should be candidates for intervention, and also on how to determine forms of intervention that may be beneficial. It is clear that support, particularly in the form of perception of available support, is important for psychological outcome following disaster. However, many questions remain concerning formalised support, and the role of supportive intervention. Aim: To investigate the impact of a disaster on the psychological health of survivors of the 2004 Indian ocean tsunami, with special consideration of types of exposure, risk factors, and the role of social support for recovery. Methods: The study is based on a questionnaire collected 14 months after the disaster from 1 505 citizens of Stockholm who were in the disaster area. Different disaster exposures were categorised and controlled for in all analyses along with sociodemographic variables. In addition, in Study IV, a population survey of Stockholm was used for comparison, and participants were matched on 8 variables. Main outcomes in all four studies were psychological distress and posttraumatic ...