Social and Mental Health Impact of Nuclear Disaster in Survivors: A Narrative Review

This narrative review synthesizes the literature on the psychological consequences of the Three Mile Island nuclear accident of 1979, the Chernobyl nuclear disaster of 1986, and the Fukushima nuclear disaster of 2011. A search was conducted on OVID for studies in English from 1966 to 2020. Fifty-nine studies were included. Living through a nuclear disaster is associated with higher levels of PTSD, depression, and anxiety. Decontamination workers, those living in closest proximity to the reactor, and evacuees experience higher rates of mental health problems after a nuclear disaster. Those with greater psychological resilience and social supports experience lower rates of psychological distress. Individual-level interventions, such as mindfulness training, behavioral activation, and cognitive reappraisal training, have shown modest benefits on improving psychological wellbeing. At the population level, many of the measures in place aimed at reducing exposure to radiation actually increase individuals’ anxiety. Technology-based supports have been studied in other types of natural disasters and it may be beneficial to look at mobile-based interventions for future nuclear disasters.


Introduction
Although nuclear disasters have been relatively uncommon throughout history, their psychological impact is long-lasting and widespread. This paper will describe the sequelae of mental health conditions related to nuclear disasters that led to actual or threat of radiation exposure. This paper includes data from the Three Mile Island accident of 1979, the Chernobyl disaster of 1986, and the Fukushima Daiichi nuclear disaster of 2011. This paper will not include exposure to radiation from medical means or nuclear warfare.
Research on the psychological impact of nuclear disasters began in the aftermath of the Three Mile Island accident, which occurred in Pennsylvania in 1979. This was a level 5 nuclear disaster on the International Nuclear Event Scale (INES). In the initial period after the accident, Three Mile Island residents received contradictory information about radiation exposure and an evacuation advisory was released for pregnant women and families with young children [1]. Although a radiation leak did occur from the plant, there has been no evidence to suggest that any residents of Three Mile Island were exposed to high enough levels of radiation to cause physiological consequences [1]. Nonetheless, the threat of radiation exposure still contributed to mental health distress in the residents of Three Mile Island [1][2][3][4][5][6][7].
The Chernobyl disaster was the first level 7 nuclear disaster in history and remains the biggest nuclear disaster to date. Despite the magnitude of this disaster, research on the Chernobyl nuclear disaster is limited as research coming out of the Soviet Union during this time period was restricted. Research on the physiological consequences of the Chernobyl nuclear disaster indicates several thousand thyroid cancer cases directly attributable to the disaster, increased prevalence of leukemia among decontamination workers, and

Inclusion and Exclusion Criteria
This review includes articles published in English between 1966 and 2020. We only included articles with a study population of adults who lived through a nuclear disaster. This excluded 11 studies on children, eight on animals, and two on people who did not experience a nuclear disaster firsthand. Thirty-four articles were excluded because of publication type. Editorials, letters to the editor, policy papers, case reports, news articles, conference presentations, and research studies that were purely qualitative in nature were excluded.
For inclusion in this review, the source of radiation in the study had to be from a nuclear disaster. This excluded 64 articles that pertained to radiation exposure from oncology treatments, medical imaging, and other types of medical radiation. We excluded three studies on radiation secondary to the atomic bombings of Hiroshima and Nagasaki in 1945 and one study on a radioactive contamination accident secondary to stolen radiotherapy equipment in Goiania in 1987. Four articles were excluding for studying microwave radiation, tanning beds, or mobile phone radiation.
We defined the outcome measures as "psychological consequences", including, but not limited to, psychiatric diagnoses such as PTSD, depression, or anxiety, or clinically significant symptoms pertaining to these diagnoses. Two articles were excluded because they only studied acute stress in the peritraumatic period and did not address any other psychological consequences. We excluded studies with primarily physiological consequences as their outcomes. We also excluded studies that had "general psychological distress" as their only outcome measure pertaining to mental health. This further limited the search by 26 papers. After applying the inclusion and exclusion criteria to the search results, 59 studies were included in this review.

Inclusion and Exclusion Criteria
This review includes articles published in English between 1966 and 2020. We only included articles with a study population of adults who lived through a nuclear disaster. This excluded 11 studies on children, eight on animals, and two on people who did not experience a nuclear disaster firsthand. Thirty-four articles were excluded because of publication type. Editorials, letters to the editor, policy papers, case reports, news articles, conference presentations, and research studies that were purely qualitative in nature were excluded.
For inclusion in this review, the source of radiation in the study had to be from a nuclear disaster. This excluded 64 articles that pertained to radiation exposure from oncology treatments, medical imaging, and other types of medical radiation. We excluded three studies on radiation secondary to the atomic bombings of Hiroshima and Nagasaki in 1945 and one study on a radioactive contamination accident secondary to stolen radiotherapy equipment in Goiania in 1987. Four articles were excluding for studying microwave radiation, tanning beds, or mobile phone radiation.
We defined the outcome measures as "psychological consequences", including, but not limited to, psychiatric diagnoses such as PTSD, depression, or anxiety, or clinically significant symptoms pertaining to these diagnoses. Two articles were excluded because they only studied acute stress in the peritraumatic period and did not address any other psychological consequences. We excluded studies with primarily physiological consequences as their outcomes. We also excluded studies that had "general psychological distress" as their only outcome measure pertaining to mental health. This further limited the search by 26 papers. After applying the inclusion and exclusion criteria to the search results, 59 studies were included in this review.

Results
Tables 1-3 summarize the key literature on the psychological consequences of nuclear disasters.    Post-traumatic stress response symptoms decreased over time but remained elevated three years after the nuclear disaster. Behavioural activation was associated with lower psychological distress and less physical symptoms at the one-month follow-up, but not at three months. Behavioural activation was associated with higher life satisfaction and increased liveliness at the three-month follow-up.  Higher health literacy was associated with lower radiation anxiety in both areas and associated with lower discrimination and prejudice in the evacuation areas. Certain radiation countermeasures were associated with lower well-being (thyroid exam, food inspection, explanatory meetings), but the basic survey was associated with greater well-being. The thyroid exam is associated with less radiation anxiety.  Utilizing rumours as a source of information about the disaster increased radiation anxiety. Attending a seminar on radiation reduced radiation anxiety.

Discussion
The literature on the mental health consequences of nuclear disasters revealed increased prevalence of PTSD, depression, and anxiety. Each of these conditions has associated risk factors and will be discussed in turn. Vulnerable populations and protective factors will be identified because this can help policymakers know where to first allocate services in the aftermath of a nuclear disaster. Although there has been a limited amount of research on interventions aimed at mitigating psychological distress after a nuclear disaster, three interventions with modestly positive outlines will be discussed. Populationlevel interventions, such as radiation countermeasures and media strategies, are outlined. Technology-based supports, such as supportive text messages, that have been successful in the aftermath of other disasters are discussed. Significant limitations are discussed and suggestions for future research are provided.

Post-Traumatic Stress Disorder (PTSD)
Stress often peaks during disaster-related events, remains high for a period of time afterwards, and then, gradually decreases [22,26,35,53,55,60]. Lasting symptoms of stress can include hypervigilance, avoidance of reminders of the event, flashbacks, and nightmares. These symptoms may bother people for years after the traumatic incident. PTSD symptomatology rates range from 33.2 to 59.4% in the first year after experiencing a nuclear accident [44,62].
Not everyone who lives through a nuclear disaster is affected the same way. There are individual variables and disaster-related variables that play a role in the psychological outcomes. Individual variables, such as social isolation [62] and having a pre-existing physical or mental illness [59,62], were associated with higher levels of PTSD. People who experienced discrimination or slurs in the aftermath of a nuclear disaster had higher levels of post-traumatic stress [59,60] and a more prolonged course of post-traumatic stress response symptoms [35]. Concern about livelihood and lost jobs were also associated with PTSD [62].
Disaster-related variables, such as witnessing the plant exploding and experiencing life-threatening danger, were associated with a more prolonged course of post-traumatic stress response symptoms [35]. Higher levels of stress experienced at the time of the nuclear disaster, or in the immediate aftermath of the disaster, have been linked to higher levels of stress a year after the disaster [59,60].
Greater exposure to radiation was associated with greater PTSD symptoms both in the year after the accident and 18 years after the accident [25]. Even if there is no actual radiation exposure, living next to a nuclear reactor that has been experiencing problems leads to higher levels of stress than living next to a normally functioning nuclear plant [1,2]. People required to evacuate their homes due to a nuclear disaster are at a higher risk of developing post-traumatic stress response symptoms [35] and are more likely to fit the criteria for a formal PTSD diagnosis [20,21,53]. Evacuees face the compounded risk of greater exposure to radiation due to their location, the stressors of relocation [20], and fear of future nuclear events.

Depression and Suicidality
Depression is also more prevalent in the aftermath of a nuclear disaster. Studies have found that 21.1-66.8% of people experience depressive symptoms [37,44] and 7.1-23% of people meet criteria for a full diagnosis of depression [7,47,61] in the first year after a nuclear accident.
Disaster-related stressors that were associated with greater depressive symptoms were having to evacuate one's home due to a nuclear disaster [20,42], income reduction, and home water incursion [47]. People with a history of psychiatric illness are also more likely to screen positive for depression in the aftermath of a nuclear disaster [4,31].
Proximity to the nuclear plant and radiation exposure are associated with depression. Those who lived closest to the nuclear reactor reported greater levels of depressive symptoms [37] and had higher rates of depression [61]. Clean-up workers in Chernobyl who experienced acute radiation sickness (ARS) were more likely to experience depressive symptoms than clean-up workers who did not experience ARS [19]. More specifically, a more significant received dose of external radiation exposure was associated with more depressive symptoms, a formal diagnosis of depression, and the severity of the depression [19]. More Chernobyl clean-up workers experienced depression and suicidal ideation after the accident than a control group of non-clean-up workers from the same area, and this pattern was consistent even 18 years after the incident [25].
Suicidal ideation is often discussed in the context of depression but has been less studied in the nuclear disaster literature. One study found that two years after the Fukushima nuclear accident, 8.9% of public employees were considered to have a "suicide risk" [49]. Chernobyl workers were more likely to report suicidal ideation than a similar group of nonclean-up workers from the Chernobyl area, with rates of 9.2% and 4.1%, respectively [25]. In addition to increased suicidal ideation, rates of suicide attempts and deaths by suicide were also impacted by the nuclear disaster. The risk of non-fatal suicide attempt via high mortality means (jumping from a significant height, hanging, or stabbing) was significantly higher for four months after the disaster and then decreased to baseline [29]. Rates of completed suicide were affected on a more long-term scale. Men from Estonia who participated in the Chernobyl clean-up had an increased risk of death by suicide compared to a control group from Estonia, but no increase in overall mortality rate 17 years after the accident [27]. In Fukushima, female suicide rates started increasing 1.5 years after the nuclear disaster and male suicide rates started increasing 2.5 years after the accident, although they had initially increased for a brief period immediately after the accident before returning to baseline [56]. For men, changes in suicide rate differed based on age group [56]. Suicide rates decreased for men 50-69 and increased for men younger than 30 and 70 and older [56].

Anxiety Disorders
In addition to anxiety-related to post-traumatic stress disorder and its associated symptoms, nuclear disasters can contribute to other types of anxiety. This can include generalized anxiety disorder, health anxiety, and non-specific anxious symptomatology. Anxiety surrounding radiation exposure and future health consequences from radiation exposure is a large focus of research on anxiety and nuclear disasters.
Damage to one's home from the nuclear disaster and having to evacuate one's home after the disaster are associated with more significant anxiety [13,21,42,57]. People evacuated to temporary housing had higher rates of generalized anxiety disorder [42]. Radiation anxiety was also shown to be higher in evacuees than non-evacuees [13,21,42].
Anxiety in the aftermath of a nuclear disaster differs from other disasters because of the ongoing threats to health that radiation exposure holds. Rather than the disaster being a discrete stressor, the stress is ongoing due to potential future risks from radiation exposure. Common concerns from radiation exposure are thyroid cancer and other types of cancer, concern about the next generation, food contamination, soil contamination, and genetic effects [43,51]. Those who perceive the risk of radiation exposure as higher have greater levels of psychological distress [4,13,21,46,50,57]. As time passes from the nuclear accident, concern about radiation decreases [32,43].

Protective Factors and Vulnerable Populations
Research has demonstrated several protective features for those who experience accidental radiation exposure. Resilience is a protective factor for depression and PTSD after a nuclear disaster [44]. Laughter has been shown to be a protective factor for Fukushima evacuees, as it is associated with improved psychological health [53] and lower perceptions of genetic risk [50]. Research has found that medical students who volunteered in the Fukushima relief efforts did not have detrimental mental health effects [28]. This could relate to a self-selection bias, because those who volunteer for post-disaster relief work may be less likely to experience mental health concerns [28], but it could also relate to volunteers' satisfaction from being able to help in a traumatic situation rather than feeling helpless.
Social support is also a significant protective factor for those who experience a nuclear disaster [3,48,53]. For elderly people forced to evacuate to rental living conditions from the Fukushima disaster, engagement in social activities was a protective factor against the development of depression [45]. Greater social support reduced the likelihood of a diagnosis of major depressive disorder or generalized anxiety disorder after a nuclear disaster [7].
Certain vulnerable populations have been identified in the aftermath of a nuclear disaster. Although research has shown impact on areas near and far to the disaster location [38], people living closest to the reactor are disproportionally affected by a nuclear disaster [22,24]. People who are forced to evacuate their homes due to a nuclear disaster have higher levels of distress [13,20,21,26,32,35,42]. This could be due to multiple mechanisms, as evacuees are more likely to have had actual radiation exposure but are also more likely to suffer social consequences such as isolation and lost employment. People with pre-existing psychiatric conditions should also be considered as a group to monitor closely after a nuclear disaster [4].
Demographic variables, such as age and gender, may also affect how people are impacted by nuclear disasters. Most research indicates that women are at higher risk for PTSD [52,53], depression [42,45], and anxiety [57]. Other research has shown no association between gender and PTSD [62] or depression [47]. Older age tends to be associated with greater risk of adverse outcomes after living through a nuclear disaster [23,52,55,60], although not all research has shown this result [47,62]. Research has shown that older age is associated with a greater likelihood of PTSD [52,55,60], depression [45], and anxiety [33]. Although symptoms of depression and PTSD improved over time for all participants, they improved at a slower rate for people 55 and older [23]. Older age is also associated with other factors that predispose people to worse outcomes after a nuclear disaster. Many people emigrated out of the Soviet Union after the Chernobyl nuclear disaster and research has shown that immigrants aged 65 and older had more difficulty establishing social supports, finding employment, and learning the language [23]. Older decontamination workers were more likely to work in an unfamiliar environment and in inadequate working conditions [33]. All of these factors may predispose older adults to worse psychological outcomes. In contrast, one study found that younger people (age 20-39) had higher levels of depression than middle-aged and older adults [47]. Another study showed that age was not associated with an increased likelihood of a PTSD diagnosis in either direction [62].

Comparison of Three Nuclear Disasters
The Three Mile Island incident, the Chernobyl nuclear disaster, and the Fukushima nuclear disaster are the three largest and most well-studied nuclear disasters in history. Despite all three disasters involving the release of radioactive material, the events had many differences. The Three Mile Island incident was a level 5 nuclear disaster on the International Nuclear Event Scale, indicating an accident with wider consequences, whereas Chernobyl and Fukushima were both level 7 nuclear disasters, indicating a major accident. Three Mile Island residents were not exposed to levels of radiation high enough to cause physical damage and had only a brief and voluntary evacuation warning [4]. No deaths have been attributed to the Three Mile Island incident [1]. In contrast, the Chernobyl nuclear disaster had both deaths from acute radiation exposure and delayed deaths from radiation exposure [8]. The Fukushima nuclear disaster caused no deaths from acute radiation [8], but deaths did occur in the context of the larger disaster, the Tohoku earthquake and tsunami. Fukushima had a much smaller evacuation zone than Chernobyl, more successful decontamination efforts, and significantly less health effects secondary to radiation exposure [8]. Despite both being level 7 nuclear disasters, some of the differences in outcome could be reasonably attributed to learning from the mistakes of Chernobyl.
All three of the nuclear disasters are associated with adverse psychological outcomes. Each of the nuclear disasters were associated with increased symptoms of PTSD [1,2,25,34] and depression [25,27,45] when compared to a control group. Suicidal ideation, attempts, and completed suicides increased in the aftermath of Chernobyl and Fukushima [25,27]. The rates of psychological sequelae are not comparable between disasters for multiple reasons. First, much of the research on the Chernobyl nuclear disaster was conducted 11-18 years after the accident. Second, the types of control groups used in the research varied between disasters. For the Three Mile Island incident, researchers compared the residents of Three Mile Island with people who lived near normally functioning nuclear plants [1,2]. The studies on Chernobyl use decontamination workers sent to Chernobyl from other countries compared to people from the same country who were not deployed [25,27]. The studies on Fukushima compare the rates of illnesses and symptoms in the same community pre-and post-nuclear disaster [29,34].
Certain factors made people more susceptible to experiencing adverse psychological outcomes in the aftermath of a nuclear disaster. Lack of social support was associated with adverse psychological outcomes for all three nuclear disasters [3,7,23,33,45,48,62]. Certain risk factors were unique to Chernobyl and Fukushima, given that the Three Mile Island nuclear incident did not release large quantities of radiation, require decontamination workers, or have a mandatory evacuation for residents [1]. For Chernobyl and Fukushima, living closer to the reactor, engaging in work with radiation exposure, and having to evacuate one's home were risk factors for PTSD and depression [19][20][21][22]24,31,42].
One might hypothesize that Fukushima would have unique risk factors or outcomes compared to the other two nuclear disasters because of the co-occurring earthquake and tsunami, but the literature did not reflect this. The only significant risk factor that was found in Fukushima, but not the other nuclear disasters, was experiencing discrimination [59,60]. The Chernobyl nuclear disaster was caused by human error, whereas the nuclear meltdown in Fukushima was secondary to a natural disaster, yet nuclear plant workers in Fukushima still faced discrimination [59,60]. Discrimination was not a variable in the studies on Chernobyl or Three Mile Island included in this review. Only studies on the Fukushima nuclear disaster addressed protective factors and psychological interventions. This may reflect the large number of years that passed between Chernobyl and Fukushima and the advances in mental health research and treatment that occurred in that period.

Individual-Level Interventions Aimed at Mitigating Psychological Distress
People who experience nuclear disasters are more likely to struggle with lasting post-traumatic stress, depression, and anxiety. Measures and programs aimed towards mitigating the physical consequences of radiation exposure have been well-studied, but research on programs to improve psychological outcomes after a nuclear disaster has been scarce. Despite the availability of community mental health supports after a disaster, rates of service utilization have been low. In psychiatric patients, experiencing the Three Mile Island accident did not increase inpatient or outpatient service use [3]. Despite the risk of severe mental health sequelae, only 6% of nuclear plant workers from Fukushima had more than three mental health visits in the three years after the disaster [35].
Although research is limited due to the low number of nuclear disasters that have occurred in history, specific psychological interventions have been shown to be helpful in mitigating some of the negative mental health consequences of living through a nuclear disaster. These cognitive interventions include mindfulness training, behavioural activation, and cognitive reappraisal training [30,36,41]. A cross-sectional study based on online self-report questionnaires found that mindfulness has been associated with lower health anxiety and psychological distress, but not radiation risk perception [41]. This indicates that although people still perceive the same risks from radiation exposure, mindfulness training may decrease somatic symptoms by increasing one's awareness of bodily sensations [41]. A randomized control trial of a two-session behavioural activation intervention was shown to have a small but significant impact on life satisfaction and livelihood, and a more intensive program could potentially have greater efficacy [36]. Learning to successfully use cognitive reappraisal skills to reduce negative emotions and thoughts associated with disaster-related pictures is associated with fewer symptoms of depression and PTSD in a correlational self-report study [30]. If people are able to re-evaluate how they think about the traumatic event, they may be able to reduce emotional reactivity, which is associated with poorer functioning [30]. Those who tend to benefit most from cognitive interventions are educated, employed, and have multiple children [36]. These three psychological interventions were studied in the aftermath of the Fukushima nuclear disaster and provide a basis for types of interventions that could be implemented in the aftermath of future nuclear disasters.

Trust in Experts and Sources of Information
Where people seek information post-nuclear disaster and which sources of information are considered the most trustworthy can have an impact on mental health sequelae. After the Fukushima nuclear disaster, the Japanese government and the Tokyo Electric Power Company (TEPCO) were rated as low in credibility [43,57]. People who utilized the government as their main source of information had higher levels of anxiety [57]. People who reported a loss of faith in experts after a nuclear disaster had higher levels of psychological distress [5], anxiety, and depression [51]. People tended to rate mass media information sources as more reliable than government information [17], and thus, local media was utilized as a source of information more often than public relations information from the local government [16]. Improving the credibility of government information and reducing uncertainty is essential for mitigating the psychological impact of radiologic disasters [57]. Policies aimed towards bolstering trust in media and government sources of information may be beneficial.
Online sources of information have been examined for their associations with mental health sequelae. Some studies have found that utilizing internet sites and blogs as sources of information was associated with higher radiation anxiety [15]. Other studies found no evidence that social media was associated with anxiety about radiation risk [17]. This may indicate that anxiety is related to the type of information utilized online rather than the online form of media itself.
In-person sources have also been investigated for perceptions of trustworthiness. People rated information from family physicians and lectures held by radiation experts as the most reliable sources of information, more than any of the media or government sources [43]. Researchers suggested that this finding could be because these people are considered experts in the field of health and radiation or because in-person communication may have a greater impact on perceived trustworthiness than mass media communications [43]. Participation in a seminar on radiation health led to decreased anxiety about radiation risk [17]. Other in-person sources of information, such as citizen groups, word of mouth, and rumours, were associated with higher anxiety [15,17]. This indicates that it is likely the source of information rather than the in-person nature of the communication that is key to reducing psychological distress.

Radiation Countermeasures
Radiation countermeasures are measures implemented at the population level after a nuclear disaster to help mitigate the negative health implications of radiation exposure. The first radiation countermeasure implemented after a nuclear disaster is deploying decontamination workers to the areas with the highest radiation levels. When people evaluated the decontamination efforts of their town as successful, they reported lower radiation anxiety [14]. Unfortunately, the decontamination workers themselves face higher levels of radiation exposure and more significant psychological consequences, including PTSD, depression, and anxiety [19,25,27,33]. Specific measures must be taken to try to reduce the psychological impact of this type of work. Interventions such as training sessions, self-study materials, and wearing a mask have not been shown to decrease anxiety in decontamination workers [33]. This points to a critical area of future research.
In addition to widespread decontamination work, other radiation countermeasures are implemented to try to limit the negative impact of radiation on community members. Tools to measure an individual's current level of radiation include whole-body counts, which are a measure of internal radiation, and individual dosimeters, which are a measure of external radiation [15]. Although aimed at preventing further radiation exposure, utilization of these particular radiation countermeasures was associated with higher levels of anxiety [15,51]. Attending explanatory meetings about radiation and paying close attention to radiation levels in food were also associated with higher levels of anxiety [15,51]. This increase in anxiety could be due to the countermeasures making the thought of radiation toxicity more salient in people's minds, or it could be a selection bias that people who are already more anxious about radiation seek out and utilize these countermeasures. Although the aim of these countermeasures is to improve both physical and mental health, they instead might point us to a group of people who would benefit from further psychological interventions to reduce their distress. An important area of future research could focus on how to implement these types of community-wide programs without an increase in anxiety from participation in the radiation countermeasures.

Technology-Based Population Supports
Technology is ubiquitous in most developed countries today and may provide an effective way to reach people struggling with mental health concerns after living through a disaster. Research has shown that mobile phone-based population interventions are a cost-effective and valuable way to provide accessible psychological support [63][64][65][66][67][68][69][70][71]. These types of programs have been shown to decrease stress, depression, anxiety, and alcohol abuse [64,66,67,[69][70][71]. A randomized control trial on psychiatric patients from Dublin in 2011 with dual diagnoses of depression and alcohol use disorder showed significantly reduced depressive symptoms and significantly greater abstinence from alcohol in the intervention group that received daily supportive text messages for three months compared to a control group that did not receive these messages [67]. Subsequent research found similar initial results but no lasting benefits six months after the cessation of the daily messages [70].
This type of mobile intervention has also been studied in remote populations. A mobile support program was effective in reducing depressive symptoms in Fort McMurry, Alberta, Canada, during the severe wildfires of 2016 [69]. This randomized control trial found that Fort McMurry residents diagnosed with Major Depressive Disorder who were assigned to the intervention group and received twice-daily supportive text messages for three months reported significantly lower depression scores on the Beck Depression Inventory than the control group (20.8 vs. 24.9) [69]. This program came to be known as Text4Mood, and this program was recognized as a mental health innovation by the Mental Health Innovations Network [71]. These types of mobile health interventions are useful in underserviced and remote areas where access to mental health services may be scarce or costly.
More recently, a similar program called Text4Hope has been developed and studied in Alberta, Canada. The goal of this program is to reduce psychological distress related to the COVID-19 pandemic and to promote resilience [63][64][65][66]68,71]. Text4Hope was created based on the Text4Mood mobile support program and provides subscribers with daily messages based on cognitive behavioural therapy [65]. The program was launched in March 2020, and within one week of launch, 32,805 Alberta residents had signed up for Text4Hope, indicating widespread uptake [63]. Demographic data indicate that people who self-subscribe to this program are mostly female (88%) and have an average age of 44.58 [71]. The average overall satisfaction with this program on a scale of 0-10 was 8.55 [71]. Most participants reported that the daily texts helped them cope with stress (77.1%), helped them cope with anxiety (75.8%), helped them feel connected to a support system (81%), helped them cope with COVID-related stressors (74%), and improved their mental well-being (75.6%). Two studies looking at stress measured with the Perceived Stress Scale-10 (PSS-10), anxiety measured with the General Anxiety Disorder Scale 7 (GAD-7), and depression measured with the Patient Health Questionnaire (PHQ-9) found decreased scores on all three scales in the intervention group who received the daily supportive messages compared to the control group [64,66]. Although these types of technologically based interventions have not been studied in prior nuclear disasters, they could be extremely useful to implement in the aftermath of a nuclear disaster, as they are able to be delivered remotely and would be accessible to those forced to evacuate because of the disaster.

Limitations
There were several limitations of this review. First, the majority of the studies used self-rating questionnaires to investigate symptoms of PTSD, depression, and anxiety, which are inferior to a clinical diagnosis [53]. Second, the most heavily studied nuclear disaster is the Fukushima nuclear disaster of 2011, which occurred in the wake of the Tohoku earthquake and tsunami, meaning that many people in the area experienced the stress of more than one type of disaster. Although this paper excluded studies that focused solely on the tsunami or earthquake, the effects of these disasters could not be controlled for and may have impacted those who experienced the nuclear disaster. Third, there are some limitations that are inherent to studying nuclear disasters, including both the difficulty finding 'healthy controls' sharing the same situation and the challenges in doing a pre-post design. Fourth, none of the reviewed literature addressed the role of pharmacology in the treatment of psychiatric conditions associated with nuclear disasters. Fifth, there are limitations inherent to qualitative narrative reviews. Narrative reviews are more subjective than systematic reviews. We attempted to mitigate this bias by outlining our search strategy and clearly stating our study inclusion criteria. Given the qualitive nature of this review, the goal was not to analyze the selected studies, but to synthesize the available literature. A relatively small sample size of 59 studies was included in this review. We chose to exclude manual searching to prioritize transparency in our study selection, but this may have limited the sample size by inadvertently excluding gray literature. Sixth, the studies addressing radiation exposure level did not use actual radiation measurements. They instead approximated higher or lower radiation exposure groups based on location of residence [22][23][24]31], evacuee status [13,16,26,49], or employment [19,23,25,26,33,52,59]. The lack of research on individual doses of radiation exposure and mental health outcomes makes it difficult to determine whether the symptoms are from the physiological impact radiation has on the brain or from the significant stress surrounding the event, which is also highest for those living the closest to the reactor, those required to evacuate, and those working in the highest risk jobs, such as nuclear plant workers at the time of the accident and decontamination workers after the accident.

Conclusions and Future Research
This review summarizes the adverse psychological outcomes associated with living through a nuclear disaster. The synthesis of studies from Three Mile Island, Chernobyl, and Fukushima nuclear disasters, indicate that survivors have higher levels of PTSD, depression, and anxiety than people who did not experience a nuclear disaster. Certain groups are disproportionally impacted by mental health sequelae after a nuclear disaster, including evacuees and those living in closest proximity to the nuclear reactor. Although the rates of each of these psychiatric conditions decrease over time since the nuclear incident, the significant impact these have on individuals and society should not be overlooked.
There are psychological interventions that have shown modest benefit in reducing the adverse psychological outcomes of nuclear disasters, including mindfulness training, behavioral activation, and cognitive reappraisal training. Research into these types of interventions in the aftermath of a nuclear disaster has been scarce; thus, further research in this area would be beneficial prior to the next large-scale nuclear disaster. Government-level interventions providing the public with credible sources of information in the aftermath of a nuclear disaster reduce fear surrounding radiation exposure. Although necessary, some of the measures that are put in place to mitigate the risk of radiation exposure in affected areas actually raise levels of mental health distress. Research could be carried out to see if there are any effective strategies to mitigate the rise in psychological distress due to the necessary radiation countermeasures. Suggestions for future research include technology-based interventions, such as mobile support programs, which are cost-effective strategies to reach large populations in geographically distributed areas.