BackgroundFollowing the Great East Japan Earthquake on March 11, 2011, the nuclear disaster at the Fukushima Daiichi Nuclear Power Plant has continued to affect the mental health status of residents in the evacuation zone. To examine the mental health status of evacuee after the nuclear accident, we conducted the Mental Health and Lifestyle Survey as part of the ongoing Fukushima Health Management Survey.MethodsWe measured mental health status using the Kessler 6-item psychological distress scale (K6) in a total of 73,569 (response rate: 40.7%) evacuees aged 15 and over who lived in the evacuation zone in Fukushima Prefecture. We then dichotomized responders using a 12/13 cutoff on the K6, and compared the proportion of K6 scores ≥13 and ≤12 in each risk factor including demographic information, socioeconomic variables, and disaster-related variables. We also performed bivariate analyses between mental health status and possible risk factors using the chi-square test. Furthermore, we performed multivariate regression analysis using modified Poisson regression models.ResultsThe median K6 score was 5 (interquartile range: 1–10). The number of psychological distress was 8,717 (14.6%). We found that significant differences in the prevalence of psychological distress by almost all survey items, including disaster-related risk factors, most of which were also associated with increased Prevalence ratios (PRs). Additionally, we found that psychological distress in each evacuation zone was significantly positively associated with the radiation levels in their environment (r = 0.768, p = 0.002).ConclusionThe earthquake, tsunami and subsequent nuclear accident likely caused severe psychological distress among residents in the evacuation zone in Fukushima Prefecture. The close association between psychological distress and the radiation levels shows that the nuclear accident seriously influenced the mental health of the residents, which might be exacerbated by increased risk perception. To provide prompt and appropriate support, continued psychosocial intervention for evacuees is strongly recommended.

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We investigated the psychometric properties of the Japanese version of the Posttraumatic Stress Disorder Checklist–Stressor Specific Version (PCL-S) using baseline data from the Fukushima Health Management Survey. A total of 26,332 men and 33,516 women aged 16 and above participated in this study. Participants lived in the Fukushima evacuation zone in Japan and experienced the Great East Japan Earthquake and nuclear power plant (NPP) incident. The PCL-S was used to assess participants’ posttraumatic stress disorder (PTSD) symptoms. In addition, we described participants and tested the validity of the PCL-S by administering the Kessler Six-item Screening Scale for Psychological Distress (K6) and assessing education; employment; self-rated health; sleep satisfaction; experiencing the earthquake, tsunami, and NPP incident; and bereavement as a result of the disaster. PCL-S scores exhibited a positively skewed, slightly leptokurtic distribution. Confirmatory factor analysis revealed that the five-factor model was a better fit than were the three- or four-factor models. The PCL-S and its subscales had high Cronbach’s alpha coefficients. The PCL-S scores had weak-to-moderate correlations with history of mental illness, bereavement, experiencing the tsunami, experiencing the NPP incident, self-rated health, and sleep satisfaction, as well as a strong correlation with psychological distress. There were significant gender and age differences in PCL-S scores. Overall, this study confirmed the psychometric properties of the PCL-S, including the score distribution, factor structure, reliability, validity, and gender and age differences. Thus, the Japanese version of the PCL-S would be a useful instrument for assessing the PTSD symptoms of community dwellers who have experienced traumatic events.

The mismatch negativity (MMN) provides a correlate of automatic auditory discrimination in human auditory cortex that is elicited in response to violation of any acoustic regularity. Recently, deviance-related responses were found at much earlier cortical processing stages as reflected by the middle latency response (MLR) of the auditory evoked potential, and even at the level of the auditory brainstem as reflected by the frequency following response (FFR). However, no study has reported deviance-related responses in the FFR, MLR and long latency response (LLR) concurrently in a single recording protocol. Amplitude-modulated (AM) sounds were presented to healthy human participants in a frequency oddball paradigm to investigate deviance-related responses along the auditory hierarchy in the ranges of FFR, MLR and LLR. AM frequency deviants modulated the FFR, the Na and Nb components of the MLR, and the LLR eliciting the MMN. These findings demonstrate that it is possible to elicit deviance-related responses at three different levels (FFR, MLR and LLR) in one single recording protocol, highlight the involvement of the whole auditory hierarchy in deviance detection and have implications for cognitive and clinical auditory neuroscience. Moreover, the present protocol provides a new research tool into clinical neuroscience so that the functional integrity of the auditory novelty system can now be tested as a whole in a range of clinical populations where the MMN was previously shown to be defective.