Subjective assessments of threats and their association to posttraumatic stress disorder symptoms: the case of the 2011 Japan earthquake and nuclear disaster.

To the Editor: On March 11, 2011, Japan was struck by a magnitude 9.0 Mw earthquake. The results were severe, as more than 15,000 people were killed by the earthquake and the following tsunami.1 The aftermath of the disaster was a level 7 nuclear meltdown in Fukushima, matching only the Chernobyl disaster.1,2 However, a recent report of the World Health Organization showed that, to date, no deaths from immediate exposure to radiation were detected and that the deaths of the 6 workers in the nuclear facility at Fukushima were not related to direct exposure to radioactive radiation.3 Moreover, the media coverage of the nuclear threat led to mass panic among the Japanese population and triggered memories of Hiroshima and Nagasaki.4,5 The media’s focus on the nuclear threat is important to note in light of the fact that although more than 15,000 people were killed during the earthquake and subsequent tsunami, no fatalities were detected from direct exposure to radioactive radiation. We conducted a study to address the lacuna in the literature concerning the subjective assessment of threat and the reactions elicited from it. Our aim was to examine if there is a potential difference in the subjective assessment of the levels of 2 threats, natural disaster versus nuclear disaster, and whether the 2 types of threat show different associations with posttraumatic stress disorder (PTSD) symptoms. On the basis of previous study,6 we hypothesized that subjective threat assessment of nuclear disaster will be higher than subjective threat assessment of natural disaster. In addition, we hypothesized that the association between subjective threat assessments of nuclear disaster and PTSD symptoms would be stronger than the association between threat assessments of natural disaster and PTSD symptoms, controlling for exposure level.