Lars Wahlstrom from Sweden's Karolinska Institutet has been looking into the mental health of Swedish people who survived the Boxing Day tsunami in 2004. His study surveyed around 1,500 people from Stockholm who had been in the disaster area. Around 70% reported that they had recovered relatively well and most were satisfied with the support that they had received, the most important source of which was family and friends. However, about 30% of those who were in the disaster area continued to experience pyschological symptoms including post-traumatic reactions, mood disturbances and sleep problems. 20% of those who were still unwell had NOT been directly exposed to the wave, severely injured or lost a loved one but had still experienced the situation as life-threatening - something that was enough to still be causing psychological problems over a year later.
You can find out more about this research by clicking on the title of this post.