Background

On March 11, 2011, a 9.0-magnitude mega-earthquake hit the islands of Japan at 2:46 pm local time. This earthquake was the strongest recorded earthquake in the country’s modern history [1]. The earthquake’s epicenter was located approximately 80 km off the northeastern (Tohoku) region of the island of Honshu, the country’s main island. Repeated aftershocks and towering tsunami waves occurred after the mega-earthquake; the tsunami waves were as high as 40 m above sea level and reached 10 km inland (Fig. 1) [2]. A large majority of the damage occurred in three prefectures in the Tohoku area: Iwate, Miyagi, and Fukushima (Fig. 2). As of December 10, 2014, the numbers of dead, missing, or injured were 15,889, 2594, and 6152, respectively [3].

Fig. 1
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Locations of earthquake epicenter of the 2011 Great East Japan Earthquake and major cities

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Fig. 2
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Three severely affected prefectures of the Tohoku region, Japan; Iwate, Miyagi, and Fukushima

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In Fukushima, the earthquakes and tsunamis triggered a nuclear accident at Tokyo Electric Power Company (TEPCO) Fukushima Daiichi Nuclear Power Plant. Between March 11 and 15, 2011, four of the six reactors experienced explosions, and three reactors escalated to nuclear meltdown and released radioactive materials, requiring a mandatory evacuation of the surrounding region. This crisis became the largest nuclear accident since the 1986 Chernobyl nuclear disaster, and the second accident, after Chernobyl, to measure Level 7 on the International Nuclear Event Scale.

On March 12, 2011, the Japanese government ordered mandatory evacuation of residents in the 20 km radius of the nuclear plant. As of December 2014, more than 121,000 residents are still on evacuation status [4]. Although there have been no fatalities owing to radiation exposure, safety concerns related to nuclear contamination created enormous fear, burden, and disruption to individuals, groups, communities, and local/national governments. These series of disasters were eventually named as the Great East Japan Earthquake (GEJE).

When evaluating post-disaster outcome studies, it must be noted every disaster is different in the terms of disaster type (e.g., natural, technological, manmade), location (e.g., developed vs. developing country), population (e.g., adults vs. children), intensity (life-threatening vs. non-), exposure frequency (e.g., single vs. repeated experiences), and many other medical/social/economic conditions. It is also very rare to randomize study samples or to have pre-disaster comparison [5].

Given these limitations, researches have shown a large majority of the people affected by disasters is resilient and will fully recover from their traumatic experiences [6]. A small portion of the affected individuals will result in a wide range of mental, behavioral, and physical health consequences [e.g., depression, posttraumatic stress disorder (PTSD) and other anxiety disorders, suicidal behaviors, alcohol misuse, and sleep disturbances]. Studies also have highlighted at-risk populations for adverse outcomes, such as female gender, preexisting psychiatric illnesses, presence of children in the home, secondary stressors, and low psychosocial resources [5–7]. Disaster workers, exposed to a variety of traumatic exposure through their work roles, are of significant concern when considering post-disaster mental health [5]. This trend was true for the Chernobyl first responders and clean-up workers as well; their depression and PTSD rates remained high two decades later [8].

A wide majority of these studies revealed the impact on mental health and psychosocial aspects of one particular event (e.g., man-made or natural). However, in the case of large-scale compound disasters, the epidemiological data are scarce. As of writing, GEJE mental health studies are evolving, but scientific review of this disaster’s mental health studies is warranted to increase better understanding of psychosocial outcomes of the people affected by the GEJE.

The aims of this article are to (1) consolidate quantitative and qualitative studies examining mental health and psychosocial impacts in people affected by the GEJE, (2) identify their mental health and psychosocial consequences, (3) ascertain vulnerable populations, and (4) elucidate factors that impact mental health and psychosocial outcomes in populations affected by the earthquake.

Methods

A systematic literature review was conducted of quantitative research articles addressing mental health of survivors and the psychological impact of the 2011 GEJE between March 2011 and December 2014. PubMed, PsychINFO, and EMBASE databases were searched with guidance on literature review method [9]. The searched keywords included Great East Japan Earthquake Disaster, Japan, disaster, health, mental health, psychological, impact, stress, trauma, bereavement, and grief and these items were used either alone or in combination.

All identified articles were examined with the title and abstract whether the article specifically addresses mental health and psychosocial issues related to the GEJE by the investigators (NH and JS). If the abstract unclearly described the study aims, method, or results, NH and JS read the article to determine the relevance of the article. Studies written in a language other than English, situational reports, activity reports, conference reports/abstracts/summaries, letters to the editor (including replies), and bulletins from universities or private organizations were not included in this review. To ensure inclusiveness, the other authors of the current article were encouraged to search for articles manually and, if additional articles met the inclusion criteria, such articles were also included for review.

A total of 382 studies were identified, with 49 articles meeting the inclusion criteria. The identified articles were categorized by four main research topics: (1) mental health outcomes among affected populations (excluding Fukushima), (2) Fukushima resident studies, (3) disaster and support worker researches, and (4) grief studies. We decided to separate the first two topics because of the uniqueness of nuclear disaster and a potentially profound mental health impact among the affected people.

Results

Table 1 summarizes the study results of mental health outcomes among the affected populations (excluding Fukushima). A total of 28 articles met this inclusion criterion [10–37]. A majority of the study populations were from Miyagi and Iwate [15 (53.6 %) and 3 (10.7 %), respectively]. Other studies included subjects from the Ibaraki, Tochigi, Tokyo, among others. A major portion of the studies were cross-sectional. Regarding outcome measures, nine (32.1 %) studies addressed PTSD, six (21.4 %) assessed general psychological distress, two (7.1 %) examined depressive symptoms. Other outcomes included anxiety, sleep disturbance, social functioning, social isolation, admission rates, suicide rates, and cerebral structure changes.

Table 1 Mental health outcomes among individuals affected by the GEJE (excluding Fukushima)
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Table 2 compiles the 12 study results reporting psychosocial consequences of the individuals affected by the Fukushima nuclear disaster [38–49]. Adverse outcome measures were primarily general psychological distress, symptoms of PTSD, depression, as well as anxiety disorders, especially in context with radiation fear. Other outcomes represented the uniqueness of a nuclear disaster, such as concern of radiation and food safety [43, 49], maternal anxiety (including food safety, outdoor safety, radiation effects on embryos, economic issues, distrust towards information disclosure) [47, 49], lowered maternal confidence [47], and stigma owing to their radiation exposures [48].

Table 2 Mental health outcomes of Fukushima residents following the GEJE
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Table 3 represents eight study outcomes of GEJE disaster and support workers [50–57]. Their outcomes measures were general psychological distress as well as symptoms of PTSD or depression. Of note, a study of Fukushima nuclear plant workers showed discrimination/slurs experience as a key factor for their mental health consequences [56]. This trend was associated with the public criticism to the electric company’s post-disaster management. One study focused on potential of fish oil in attenuating PTSD symptoms among DMAT (Disaster Medical Assistant Team) medical workers [53].

Table 3 Studies of the GEJE disaster and support workers
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Table 4 shows a result of a sole study examining the grief responses affected by the GEJE [58]. This study showed the distinctiveness of complicated grief from symptoms of PTSD or depression. Other articles, not listed in the table, were leaned on narratives and support activity reports. For example, our co-author (ST) launched a support group immediately after the disaster for people in grief and bereavement [59]. This support group aims to (1) provide information about grief, the concept of which is not as popularly known in Japan (much like PTSD), and (2) provide training sessions and workshops in collaboration with the local grief support organizations.

Table 4 Grief study following the GEJE
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Discussions

Our review compiled a wide array of mental health consequence following the GEJE, an unprecedented compound disaster with a combination of earthquakes, tsunamis, and a series of nuclear accidents. A considerable proportion of the study population was mentally affected to a substantial degree, and mental health responses ranged from approximately one-tenth to nearly half of the respondents [12, 27]. Mental health outcomes included, but were not limited to, PTSD, depression, and anxiety. Physical health changes, such as sleep and eating disturbances, were also reported.

Although every disaster is different, disasters are large-scale, stressful, and distressing events that affect a significant number of people. Those who experience higher exposure to traumatic events are likely to show higher mental health responses (i.e., dose–response relationship) [60]. For the most people, these acute responses are normal and gradually decrease over time, but a small proportion of the affected individuals will suffer long-term mental health issues. In a review of 160 disaster mental health studies, proportions of subjects with severe impairment were 21.6 % for natural disasters and 18.5 % for technological disaster samples [6]. The articles in this review had relatively higher mental health rates than in previous studies. This trend might be related to the high impact of this disaster as well as the GEJE study timing, because most of the studies were conducted among the direct victims within 2 years after the disaster. Long-term, longitudinal studies are evolving, and they will potentially be useful to understand the trajectories of mental health consequences among these people.

In the region affected by the Fukushima nuclear disaster, invisible and imperceptible nature of radioactive materials has been challenged among the affected people. The residents’ responses were diverse and complex; along with high proportions of mental health distress among the Fukushima residents [46], concerns for radiation effect were a prominent concern especially among pregnant women and mothers of young children [43, 49, 61]. Safety issues in food and outdoor activities, along with economic issues and distrust in information disclosure were also reported [43, 49]. Public psychosocial responses such as discrimination and stigmatization were also reported [48, 56].

These findings are in accordance with a series of Chernobyl studies where a complex relationship between radiation exposure and physical/mental health effect has been an ongoing debate. Physical outcome studies tend to be controversial, although firm evidence can be found only on the deaths of first responders due to acute radiation exposures and high prevalence of thyroid cancer among the exposed children [8]. Still, psychosocial and economic disruptions to the affected people were significant, and the International Atomic Energy Agency regarded mental health as the major public health sequelae of the Chernobyl accident [62]. Mothers of young children and plant clean-up workers were among the two groups of particular concern [63–65]. Psychosocial issues included not only mental health disorders but also stigmatization and discrimination of the affected people [8], suggesting the importance of integrity and accuracy of information as well as risk communication strategies.

Two Fukushima studies reported distress among internally displaced people [38, 41]. Mandatory evacuation measures have been in place for the area surrounding the nuclear plant, and the evacuees potentially have uncertain and ambiguous perspectives on whether or not they will be able to return home [66]. This trend was also compatible with Chernobyl studies reporting challenges in evacuation and resettlement [8]. Future studies will be essential to clarify the effect of evacuation following nuclear disasters.

Fukushima and Chernobyl studies suggest that substantial public health efforts are crucial to establish a system capable of such exposures. Integrity and accuracy of information will be a critical issue for the public to assess their health status. These studies also have implications for other “tangible” disasters, such as emergencies related to bio-chemical weapons and infectious diseases [67]. Long-term studies will be important to increase the psychosocial impact among Fukushima residents, with special focus on children, mothers, and nuclear plant workers.

A number of studies assessed a considerable degree of mental distress among disaster workers. This is likely to be owing to work-related exposures of these workers. In the case of GEJE, many of the workers were also local disaster victims, and had struggles as survivors along with their work-related exposures. This effect was prominent in several studies [51, 56, 57]. Two worker studies identified experiences of being discriminated against and handling residents’ complaints as risk factors for their adverse mental health [56, 57]. In the former study, the Fukushima nuclear plant workers became targets of public criticism because their company was blamed for their post-disaster mismanagement. In the latter, Miyagi Prefecture workers received direct complaints from their residents in a chaotic situation. These results might give hypotheses that mental health of disaster workers is susceptible to their stakeholder’s criticisms.

Past literatures identified mortuary work as predictors of PTSD or physical symptoms among disaster workers [68, 69], but in our review, there has yet be an evidence that mortuary work was associated with adverse mental health [50, 51]. Further studies will be needed to elucidate the relationship between dead body exposure and mental health outcomes among this population.

Previous studies highlighted vulnerable populations for post-disaster mental health, such as children, evacuees, the bereaved, and individuals with preexisting physical/mental health conditions [5, 6]. Our compilation overall shows a similar trend, although studies are relatively few, especially in the context of grief.

We recognize several limitations of this paper. The GEJE, especially the Fukushima nuclear accident, is an ongoing disaster, and new studies are emerging. Given the timing and methodology of our literature search, we were not able to include narrative studies, non-English papers, or papers describing long-term disaster impact. Although we made every possible effort to include all related studies, some studies may have been inadvertently omitted.

Given these limitations, this literature review encompasses research on the mental health trajectories of people affected by the GEJE, a complex earthquake/tsunami/nuclear disaster. Along with our review, future studies will be essential for having a better understanding of this disaster, and especially for ascertaining the long-term outcomes and their correlates.