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Published in final edited form as: Soc Sci Med. 2021 Feb 13;273:113777. doi: 10.1016/j.socscimed.2021.113777

Dispositional Optimism and Disaster Resilience

A natural experiment from the 2011 Great East Japan Earthquake and Tsunami

Krisztina Gero a,b,*, Jun Aida c, Kokoro Shirai d, Katsunori Kondo e,f, Ichiro Kawachi a
PMCID: PMC8005486  NIHMSID: NIHMS1677923  PMID: 33639358

Abstract

Objective.

Dispositional optimism – the general belief that good things will happen – is considered a key asset for the preservation of mental health after a traumatic life event. However, it has been hypothesized that in extreme situations such as major disasters where positive expectations cannot overcome the grim reality on the ground, being optimistic might be a disadvantage. To test this mismatch hypothesis, this study explores whether higher pre-disaster dispositional optimism is associated with higher posttraumatic stress (PTS) and depressive symptoms among individuals who experienced the 2011 Great East Japan Earthquake and Tsunami.

Methods.

Information on optimism was collected from community-dwelling residents aged ≥65 years seven months before the 2011 Earthquake/Tsunami in Iwanuma, a Japanese city located 80-km from the epicenter. Data on disaster-related personal experiences (e.g., loss of relatives or friends/housing damage), as well as depressive and PTS symptoms, were collected during a follow-up survey in 2013, 2.5 years after the earthquake and tsunami. Multiple logistic regression models were utilized to evaluate the associations between disaster experiences, optimism, and depressive/PTS symptoms among 962 participants.

Results.

Higher pre-disaster dispositional optimism was associated with lower odds of developing depressive symptoms (OR=0.78, 95% CI: 0.65 to 0.95) and PTS symptoms (OR=0.83, 95% CI: 0.69 to 0.99) after the earthquake. Contrary to the mismatch hypothesis, high dispositional optimism buffered the adverse impact of housing damage on depressive symptoms (interaction term coefficient=−0.63, p=0.0431), but not on PTS symptoms.

Conclusions.

In contrast to the mismatch hypothesis, the results suggest that dispositional optimism is a resilience resource among survivors of a disaster.

Keywords: Disasters, Optimism, Hope, Posttraumatic Stress Disorder, Depressive Symptoms

Introduction

Every year, around 160 million people are affected by disasters worldwide (WHO, n.d.). In the face of such adversities, resilience – the capacity to overcome a traumatic life event – is crucial for survivors (Aldrich, 2012; Connor and Zhang, 2006; Iacoviello and Charney, 2014). A growing body of evidence points towards dispositional optimism – the general belief that good things will happen – as a key asset in the prevention of deteriorating health after a distressing experience (Ahmad et al., 2010; Carbone and Echols, 2017; Connor and Zhang, 2006; Gargano et al., 2019; Iacoviello and Charney, 2014; Sumer et al., 2005).

By promoting positive expectations about the future, optimism is thought to lead to increased efforts to achieve desired goals and more successful coping strategies to manage stress (Nes and Segerstrom, 2006). Optimistic people are thought to be more likely to look for and to have a higher perception of social support, while they also tend to emphasize the positive aspects of a stressful situation, which might protect them against the harmful psychological effects of a traumatic experience (Gargano et al., 2019; Lowe et al., 2013; Nes and Segerstrom, 2006; Prati and Pietrantoni, 2009).

In accordance with this hypothesis, several previous studies have linked higher optimism to better health outcomes after disasters, including lower risks of psychological distress, posttraumatic stress disorder (PTSD), depressive symptoms, and generalized anxiety (Ahmad et al., 2010; Carbone and Echols, 2017; Gargano et al., 2019; Sumer et al., 2005). Apart from directly influencing distress levels, optimism has been also shown to moderate the association between stress and deteriorating mental health (Cozzarelli, 1993; Sumer et al., 2005). In addition, cognitive behavior therapy targeted toward increasing positive attitudes has been shown to successfully decrease depressive symptoms, suggesting that optimism is a modifiable personal resource for coping with adverse psychological responses (Geschwind et al., 2019).

In recent years, however, a contrasting theory has emerged to challenge the foregoing account of the salutogenic effects of optimism. Building on evidence from the fields of developmental and evolutionary psychology (Boyce and Ellis, 2005; Brody et al., 2013; Frankenhuis and Del Giudice, 2012), the alternative theory posits that high expectations towards one’s future might be actually harmful to mental health if those expectations cannot be met due to overwhelming experiences of trauma (Fletcher, 2018; Nederhof et al., 2014). Following this mismatch theory, a prospective study of the 9/11 terrorist attack found that young adults who were the most hopeful towards the future before the attack were more likely to develop increased depressive symptoms after the incident compared to their less hopeful counterparts (Fletcher, 2018). Based on these results, it was suggested that while dispositional optimism could be beneficial in uneventful times, the same positive expectations toward the future might be harmful under extreme/high-stress situations (Fletcher, 2018).

Empirical tests of the mismatch theory remain sparse. Part of the challenge is that most studies on the associations of optimism with health after disaster have relied on either a cross-sectional design or assessed only post-disaster measures of optimism (Ahmad et al., 2010; Carbone and Echols, 2017; Gargano et al., 2019; Sumer et al., 2005). However, an individual’s sense of optimism might change due to the disaster exposure (Chiu et al., 2002). Therefore, post-disaster surveys might not accurately reflect pre-disaster attitudes.

To address the inconsistencies in the published literature, this study took advantage of a unique natural experiment in which pre-disaster information on hopefulness and optimism was collected among the residents of a community that was directly affected by the 2011 Great East Japan Earthquake and Tsunami. To test the mismatch theory, the analyses explore whether higher dispositional optimism and hopefulness measured before the disaster is associated with higher PTS and depressive symptoms after trauma exposure. Specifically, a sharp test is provided to assess whether optimism can mitigate or worsen the adverse impact of disaster experiences on the mental health of survivors.

Methods

Study Population

Data were based on the Iwanuma Study cohort (Kawachi et al., 2020), a sub-set of the Japan Gerontological Evaluation Study (JAGES), a nationwide cohort study established in 2010 to explore the social determinants of healthy aging (Kondo et al., 2018). Iwanuma City – a municipality of 44,187 residents located around 80 km to the west of the epicenter of the March 11, 2011 earthquake and tsunami – was one of the 31 participating locations. Due to the disaster, 48% of the land area was flooded, 5,542 dwelling units were damaged or destroyed, and 180 residents lost their lives in the town (Supplementary Fig.1).

In August 2010, approximately seven months before the earthquake and tsunami occurred, surveys were mailed to all Iwanuma residents aged 65 years or older (n=8,576) identified through the local residential registry. One-quarter of the sample was randomly selected to answer additional questions related to psychological resources such as dispositional optimism. The response rate was 59.0% (n=5,058) to the baseline survey, which is similar to other studies enrolling community-dwelling respondents (Santos-Eggimann et al., 2009).

In October 2013, roughly 2.5 years after the disaster, a follow-up survey was conducted among all eligible surviving study participants (n=4,380), inquiring about their current mental and physical health, as well as disaster-related personal experiences. The follow-up rate was 82.1%, consisting of 3,594 respondents. Informed consent was obtained from all participants at the time of data collection. In the current study, 27 respondents were excluded due to incompletely signed consent forms, resulting in a sample size of 3,567 participants, out of whom 962 individuals also provided information on dispositional optimism with 841 and 904 valid responses to posttraumatic stress and depressive symptoms, respectively (Supplementary Fig.2).

Posttraumatic Stress Symptoms and Depressive Symptoms

The Screening Questionnaire for Disaster-Related Mental Health (SQD) was utilized to measure symptoms of posttraumatic stress (PTS) in 2013, after the disaster. The SQD is a self-administered survey developed after the 1995 Great Hanshin Earthquake and validated showing good validity and reliability among the Japanese older population (Fujii et al., 2008). The PTS sub-scale of the SQD contains nine questions with a simple “yes” (score of 1) or “no” (score of 0) format. Summing all items, possible PTS scores ranged from 0 to 9, with higher scores indicating worse PTS symptomatology. Obtained through a receiver operating characteristic curve, the convergent validity of the PTS sub-scale for diagnosing posttraumatic stress disorder was 0.91 when compared to a Clinician-Administered PTSD Scale (Fujii et al., 2008). Based on the published literature, for easier interpretation, a binary variable was created utilizing a cut-off PTS score of ≥4 to identify moderately and severely affected participants (Li et al., 2019; Masedu et al., 2014).

The short version of the Japanese Geriatric Depression Scale (GDS-15) – a self-reported questionnaire consisting of 15 items with “yes” or “no” as possible answers – was used to assess depressive symptoms both in the baseline and follow-up surveys. Summing the scores given to each item, the possible range of the GDS-15 scale was from 0 to 15, with higher scores representing higher depressive symptomatology (Burke et al., 1991; Lyness et al., 1997). The GDS-15 scores were dichotomized using a predefined cut-off point of 5 or more to identify participants with high depressive symptomatology. With a cut-off point of 5, the GDS-15 scale had a sensitivity of 92% and a specificity of 81% for diagnosing major depression (Lyness et al., 1997).

In the final analytic sample, the Cronbach alpha was 0.75 for the SQD-PTS scale, and 0.83 for the GDS-15 scale.

Optimism and Disaster Experiences

To assess dispositional optimism, in the 2010 baseline questionnaire, respondents were asked to fill out the 6-item Life Orientation Test-Revised (LOT-R) (Scheier et al., 1994). While the original LOT-R consists of 10 questions containing four unscored filler items, in the JAGES survey, only the six main items were included to reduce the response burden on the participants. On a four-point Likert scale, possible responses to each of the questions ranged from strong disagreement (score of 0) to a strong agreement (score of 4). After summing the answers to all six items, the final scores ranged from 0 to 24, with higher values indicating higher dispositional optimism. The LOT-R has been validated in the Japanese cultural context, showing acceptable internal consistency (Nakano, 2004). The Cronbach alpha of the LOT-R was 0.57 in the final sample.

To conduct a sensitivity analysis, hopefulness was also evaluated as a crude 1-item measure of optimism, utilizing the following survey question from the GDS-15 scale: “Do you think there is no hope in your life?” The possible responses were “yes” or “no”.

In the 2013 follow-up survey, disaster-related personal experiences were also assessed, asking participants about whether they lost friends or relatives (yes or no), or suffered housing damage due to the earthquake and tsunami. Based on the reports of two independent inspectors instructed by the government, possible levels of housing damage ranged from “no damage” (score of 1) to “completely destroyed” (score of 5).

Covariates

To control for confounding, the following factors with the potential to affect both positive attitudes and mental health were included to the models: age (continuous), sex (female or male), equivalized household income (continuous), education (≤9 years or ≥10 years), marital status (married or other), and baseline depressive symptoms (score of ≥5 or score of <5) (Lyness et al., 1997; Schreiner et al., 2003).

Statistical Analysis

Missing values for optimism and disaster experiences, as well as the covariates, were replaced using sequential regression multiple imputation (SRMI, aka “imputation by full conditional specification” or “imputation using chained equations”) to account for potential bias due to missing data. The missing rate was 1.25% to 5.05% for the GDS-15 scale, 3.12% to 6.86% for the LOT-R scale, 3.73% for hopefulness, 2.83% for housing damage, and 0.10% to 12.25% for the covariates. Based on ten imputed datasets, multiple logistic regression models were utilized to estimate the associations between disaster experiences, optimism, hopefulness, and mental health.

Two sets of models were constructed for each health outcome – PTS and depressive symptoms: The first model included disaster experiences such as loss of friends or relatives and housing damage and was adjusted for age, sex, equivalized household income, education, and marital status (Model 1). The second model (Model 2) added dispositional optimism, and controlled for baseline depressive symptoms. Interaction terms between disaster experiences and mental attitudes were also tested. For easier interpretation, a binary variable was created utilizing median split to represent high (score of ≥13) versus low (score of <13) levels of optimism. All analyses were repeated after excluding participants (n=27) who provided valid responses to less than three questions of the 6-item LOT-R scale.

For the sensitivity analyses, depressive symptoms were assessed based on 14 items of the GDS-15 scale (scores ranging from 0 to 14), excluding the question on hopefulness. Considering that the mean GDS scores did not change significantly after excluding one item from the scale, the same cut-off score of ≥5 was utilized to dichotomize depressive symptoms. The Cronbach alpha of the modified GDS scale was 0.81. Models containing hopefulness were based on data from 3,567 Iwanuma participants, with 3,348 and 3,111 valid responses for PTS and depressive symptoms in 2013, respectively.

All analyses were conducted using SAS version 9.4 (SAS Institute Inc., Cary, NC) and SAS-callable IVEware (Imputation and Variance Estimation Software) version 0.2.

Results

Table 1 summarizes the pre- and post-disaster participant characteristics in the full Iwanuma sample and the dispositional optimism sub-sample of the analysis. The mean age of the respondents in the full- and sub-samples was 73.6 (standard deviation [SD]=6.3) and 74.3 years (SD=6.3), respectively. Among all participants, in 2010, 77.7% thought there is hope in their lives, while 33.2% had high depressive symptomatology. In the sub-sample, the mean pre-disaster optimism score was 12.7 (SD=2.5), with 34.4% of the participants reporting major depressive symptoms at baseline. Compared to the full sample, respondents in the optimism sub-sample were less likely to have low educational attainment (full-sample: 36.3%; sub-sample: 30.6%), and more likely to report higher equivalized household income (full-sample mean=225.3, SD=148.9; sub-sample mean=252.3, SD=173.9).

Table 1.

Characteristics of the Analytic Samples in the Baseline and Follow-up Iwanuma Surveys in 2010 and 2013

All participants from Iwanuma City (n = 3,567) Dispositional optimism sub-sample (n = 962)
n % Mean (SD) n % Mean (SD)
Baseline survey in August, 2010
Age, years 3,567 73.6 (6.3) 962 74.3 (6.3)
Sex, female 2,015 56.5 544 56.6
Equivalized household income, JPYa 3,567 225.3 (148.9) 962 252.3 (173.9)
Low educational attainment, ≤9 years 1,293 36.3 294 30.6
Marital status, married 2,528 70.9 673 69.9
Depressive symptoms, score of ≥5 1,185 33.2 331 34.4
Hopeful 2,770 77.7
Optimism, score 962 12.7 (2.5)
Follow-up survey in October, 2013
Loss of relatives and/or friends 1,329 37.3 348 36.2
Housing damage, scoreb 3,567 1.9 (1.0) 962 1.5 (0.6)
Depressive symptoms, scorec 3,111 3.6 (3.1) 841 3.7 (3.3)
Posttraumatic stress symptoms, score 3,348 2.3 (2.3) 904 2.1 (2.1)
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a

1 unit = 10,000 JPY (approximately 100 USD)

b

Housing damage scores: 1: None - 5: Destroyed

c

Depressive symptom scores in the follow-up survey were based on all 15 items of the GDS-15 scale for the dispositional optimism sub-sample, and on 14 items of the GDS-15 scale – excluding the question on hopefulness – for the full Iwanuma sample Abbreviations: GDS-15, 15-item Geriatric Depression Scale; JPY, Japanese Yen; SD, Standard Deviation; USD, United States Dollar

In the 2013 follow-up survey, the mean depressive symptom scores were similar in both samples (full-sample mean=3.6, SD=3.1 [GDS-14]; sub-sample mean=3.7, SD=3.3 [GDS-15]). However, the mean posttraumatic stress symptoms scores of the respondents (full-sample mean=2.3, SD=2.3; sub-sample mean=2.1, SD=2.1) as well as exposure to disaster experiences were slightly lower in the optimism sub-sample (full-sample: 37.3% and sub-sample: 36.2% for loss of friends/relatives; full-sample mean=1.9, SD=1.0 and sub-sample mean=1.5, SD=0.6 for housing damage).

When the associations between disaster experiences, pre-disaster dispositional optimism, and post-disaster mental health were tested (Table 2), housing damage was associated with an increase in the odds of developing higher depressive (odds ratio [OR]=1.37, 95% confidence interval [CI]: 1.06 to 1.78 in Model 1) and PTS symptomatology (OR=1.85, 95% CI: 1.36 to 2.50 in Model 1). Loss of relatives or friends also showed a positive association with an increased odds of higher PTS symptoms (OR=1.80, 95% CI: 1.30 to 2.50 in Model 1), while this association could not be observed for depressive symptoms. On the other hand, optimism showed an inverse association with both higher depressive and posttraumatic stress symptoms (OR=0.78, 95% CI: 0.65 to 0.95; and OR=0.83, 95% CI: 0.69 to 0.99 for each SD increase in optimism in Model 2, respectively). These associations did not change substantially after excluding respondents who answered less than half of the six LOT-R questions (Supplementary Table 1).

Table 2.

Associations Between Disaster Experiences, Pre-Disaster Dispositional Optimism, and Post-Disaster Mental Health, 2010–2013

Depressive Symptoms (N=276 / 841 participants) Posttraumatic Stress Symptoms (N=207 / 904 participants)
Model 1
Disaster experiences
OR (95% CI)		 Model 2
Optimism (1SD)
OR (95% CI)		 Model 1
Disaster experiences
OR (95% CI)		 Model 2
Optimism (1SD)
OR (95% CI)
Housing damage
1: None - 5: Destroyed (Continuous) 1.37 (1.06, 1.78) 1.23 (0.92, 1.65) 1.85 (1.36, 2.50) 1.79 (1.32, 2.43)
Loss of relatives and/or friends
0:No, 1:Yes 0.91 (0.67, 1.25) 0.98 (0.69, 1.40) 1.80 (1.30, 2.50) 1.91 (1.37, 2.65)
Age
Continuous 1.04 (1.02, 1.07) 1.04 (1.01, 1.07) 1.01 (0.98, 1.03) 1.00 (0.97, 1.03)
Sex
0: Male, 1: Female 1.20 (0.87, 1.65) 1.23 (0.86, 1.78) 2.03 (1.42, 2.90) 2.09 (1.45, 3.00)
Equivalized household incomea
Continuous (1SD) 0.80 (0.66, 0.98) 0.92 (0.75, 1.13) 0.97 (0.81, 1.17) 1.03 (0.85, 1.24)
Educational attainment
0: ≤9 years, 1: ≥10 years 0.94 (0.67, 1.31) 1.05 (0.71, 1.53) 0.89 (0.62, 1.28) 0.89 (0.62, 1.28)
Marital status
0: other, 1: married 0.64 (0.45, 0.90) 0.79 (0.53, 1.19) 0.90 (0.61, 1.32) 0.96 (0.65, 1.42)
Depressive symptoms
0: score of <5, 1: score of ≥5 8.60 (6.03, 12.26) 1.80 (1.27, 2.57)
Optimism
Continuous (1SD) 0.78 (0.65, 0.95) 0.83 (0.69, 0.99)
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a

1 SD = approximately 1,740,000 JPY (approximately 17,400 USD)

Abbreviations: CI, confidence interval; JPY, Japanese Yen; SD, Standard Deviation; USD, United States Dollar

Testing the interaction terms between disaster experiences and optimism (Table 3 and Figure 1), the results showed that dispositional optimism buffered the adverse effect of housing damage on depressive symptoms (interaction term coefficient=−0.63, p=0.0431), but not on PTS symptoms.

Table 3.

Assessments of Interaction Terms Between Disaster Experiences and Optimism, 2010–2013

Depressive Symptoms (N=276 / 841 participants) Posttraumatic Stress Symptoms (N=207 / 904 participants)
Coefficient (95% CI) P-value Coefficient (95% CI) P-value
Optimism*housing damagea −0.63 (−1.24, −0.02) 0.0431 0.16 (−0.49, 0.81) 0.6245
Optimism*loss of friends or relativesa 0.07 (−0.68, 0.82) 0.8569 0.15 (−0.56, 0.85) 0.6801
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All models were adjusted for housing damage, loss of relatives or friends, age, sex, equivalized household income, educational attainment, marital status, baseline depressive symptoms, and optimism.

a

Dipositional optimism scores were dichotomized utilizing median split (high optimism [score of ≥13] vs. low optimism [score of <13]).

Figure 1.

Figure 1

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Associations of Housing Damage with Depressive Symptoms According to Dispositional Optimism Levels

The probability of having high depressive symptoms associated with the severity of housing damage (1= “No damage” − 5= “Completely destroyed”) among participants with low and high levels of dispositional optimism. LOT-R scores were dichotomized by median split with a score of ≥ 13 considered as “high optimism”.

In the sensitivity analyses with hopefulness as the pre-disaster positive attitude measure (Supplementary Table 2), similar results could be observed. For depressive symptoms, the corresponding odds ratios were 1.23, 95% CI: 1.14 to 1.33 for housing damage (Model 1); and 0.66, 95% CI: 0.51 to 0.85 for hopefulness (Model 2). For PTS, the corresponding odds ratios were 1.39, 95% CI: 1.28 to 1.50 for housing damage (Model 1); 1.87, 95% CI: 1.59 to 2.21 for loss of relatives/friends (Model 1); and 0.77, 95% CI: 0.61 to 0.98 for hopefulness (Model 2). However, interaction terms between disaster experiences and hopefulness were not statistically significant for either of the two mental health outcomes (data not shown).

Discussion

The present study found that pre-disaster positive attitudes, such as hopefulness and optimism, strengthened an individual’s resilience against developing depressive and posttraumatic stress symptoms after a disaster. Also, higher dispositional optimism, though not hopefulness, mitigated the impacts of housing damage on the risk of increased depressive symptomatology.

A wide range of benefits have been ascribed to maintaining a positive mental attitude when faced with adversity, including disasters (Ahmad et al., 2010; Carbone and Echols, 2017; Gargano et al., 2019; Nes and Segerstrom, 2006; Prati and Pietrantoni, 2009; Sumer et al., 2005). However, being optimistic after a traumatic event might not be the same as having higher dispositional optimism beforehand (Chiu et al., 2002; Fletcher, 2018). According to the mismatch theory, while having a generally positive outlook in one’s life might be beneficial in several life domains, being optimistic could also prove to be a disadvantage in overwhelmingly stressful situations where positive expectations cannot hope to be met (Fletcher, 2018; Tennen and Affleck, 1987). To test the mismatch theory in a post-disaster reality, having pre-disaster information on levels of optimism is crucial. One of the key strengths of this study is that information on mental attitudes – hopefulness and dispositional optimism – was collected before disaster exposure, eliminating the potential of recall bias and providing a prospective study setting.

The current results are in line with past work reporting a positive association between higher levels of dispositional optimism and depressive or PTS symptoms among survivors of disasters (Ahmad et al., 2010; Carbone and Echols, 2017; Gargano et al., 2019; Sumer et al., 2005). Furthermore, it was also previously shown that positive mental attitudes buffered the negative impact of disaster exposure on mental health (Birkeland et al., 2017; Carbone and Echols, 2017). In a U.S. study, dispositional optimism mitigated the effect of housing damage on PTSD after a tornado outbreak (Carbone and Echols, 2017). At the same time, this association could not be observed in the same U.S. population for depression (Carbone and Echols, 2017). Apart from the different cultural contexts (the U.S. versus Japan), one of the possible explanations for the somewhat conflicting results might be the difference between the two study designs. Carbone and Echols employed a cross-sectional survey enrolling respondents aged ≥18 years – measuring both mental attitude and health post-disaster – as opposed to the current prospective study with pre-disaster information on optimism, based on an older population aged ≥65 years (Carbone and Echols, 2017). Also, the number of participants in the Iwanuma Study who provided information on pre-disaster optimism was relatively low. In addition, PTS symptoms were slightly less prevalent than depressive symptoms among the Iwanuma respondents, potentially leading to a lack of power to get statistically significant interaction terms between optimism and PTSD. Therefore, the findings should be further explored in other populations.

In testing the mismatch theory, this study failed to replicate Fletcher’s results, in which pre-disaster hopefulness was associated with increased depressive symptoms after the 9/11 terrorist attack (Fletcher, 2018). However, there were several notable differences between the two studies.: First, though both surveys had employed one item to measure hopefulness, the Iwanuma questionnaire provided only two potential responses (yes or no) as a contrast to the 4-item Likert-scale of the earlier publication. However, the main analyses were based on a sophisticated multi-item scale, confirming the positive association between higher pre-disaster optimism and better mental health after disaster exposure. Second, there were also substantial differences in the cultural context and the age of the study participants (young American adults [mean age: 21.95 years SD=1.77] versus older Japanese adults [mean age: 73.64 years, SD=6.28]). On the one hand, it has been shown that dispositional optimism increases throughout the lifespan from early adulthood, peaking around the ages of 55 to 70 before declining in later life (Chopik et al., 2015; Schwaba et al., 2019). Experiencing personal development and positive life events, such as achieving work-related accomplishments, finishing higher education, or getting married, were associated with optimism development (Schwaba et al., 2019). Also, experiencing adverse life events did not affect the trajectory of dispositional optimism during adult life (Schwaba et al., 2019). On the other hand, Americans tend to report higher mean scores on the LOT-R scale compared to Japanese, which might partly explain the differences in psychological responses between the two study populations (Kan et al., 2014). Finally, Fletcher et al. explored short term responses – within seven months – following the tragedy, while the Iwanuma follow-up survey collected data approximately 2.5 years after the disaster. It is possible that the short-term effects of trauma exposure on mental health are more severe among those who are more optimistic. In the immediate – and devastating – aftermath of a large-scale disaster, optimistic people may indeed be “crushed”. However, as the situation returns to a semblance of normality over a period of years, the direction of the optimism-trauma interaction might flip.

There are some limitations to the current study which have to be considered when interpreting the findings. First, due to the 59% baseline (pre-disaster) response rate, the possibility of selection bias has to be considered. However, the demographic profile of the participants was comparable to that of all Iwanuma residents aged 65 years or older, as previously confirmed based on government census information (Hikichi et al., 2018). Furthermore, in the published literature, other studies enrolling community-dwelling respondents had comparable response rates (Santos-Eggimann et al., 2009). Second, only one-quarter of all Iwanuma Study participants provided information on dispositional optimism, potentially leading to a lack of power in the statistical analyses. This might also partly explain the wider confidence intervals around the point estimates in the optimism sub-sample (Table 3). Therefore, the results have to be interpreted with caution. Third, the possibility of residual confounding cannot be excluded. However, controlling for sociodemographic factors, the present findings should be comparable to the existing literature on the topic (Ahmad et al., 2010; Carbone and Echols, 2017; Fletcher, 2018; Gargano et al., 2019). Fourth, in the JAGES study, only one municipality – Iwanuma City – out of the 31 participating locations was directly exposed to the 2011 earthquake and tsunami. Therefore, the results might not be nationally representative or generalizable to other disaster-affected areas. Finally, depressive and PTSD symptoms were self-reported, possibly leading to response bias due to social desirability (Fastame and Penna, 2012).

In summary, the findings suggested that hopefulness and dispositional optimism provided personal resources for the survivors to remain resilient in the face of a disaster, protecting them against declining mental health after the traumatic experience. Also, optimism could buffer the negative impact of disaster experiences – for example, housing damage – on depressive symptoms. Overall, these results suggest that strengthening optimism could contribute to disaster resilience. At the personal level, evidence-based prescriptions for building optimism have been described (Geschwind et al., 2019; Heinonen et al., 2005; Malouff and Schutte, 2017; Meevissen et al., 2011; Peters et al., 2010). At the same time, it is important to recall that strengthening optimism at the population level depends on a set of pre-conditions that protects and preserves people’s sense of ontological security. These pre-requisites include the provision of social services that meet the needs of vulnerable groups, building trust in institutions, and sound governance.

Supplementary Material

1

Highlights.

  • Examined how dispositional optimism is associated with mental health after disaster

  • Used data from a longitudinal cohort study of Japanese adults aged ≥65 years

  • Pre-disaster optimism supports resilience against depressive symptoms after disaster

  • Pre-disaster optimism supports resilience against posttraumatic stress after disaster

  • High optimism buffered the adverse impact of housing damage on depressive symptoms

Acknowlwdgements / Funding

We appreciate the support and cooperation of the Iwanuma mayor’s office and the staff of the Department of Health and Welfare of the Iwanuma city government. Funding: NIH grant R01 AG042463 and R01 AG042463-06; Grants-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (KAKENHI 23243070, KAKENHI 22390400, KAKENHI 24390469, KAKENHI 15KT0007, and KAKENHI 16KK0059); Health Labour Sciences Research Grant from the Japanese Ministry of Health, Labour, and Welfare H22-Choju-Shitei-008 and H24-Choju-Wakate-009; and grant S0991035 from the Strategic Research Foundation Grant-Aided Project for Private Universities from the Japanese Ministry of Education, Culture, Sports, Science, and Technology.

Footnotes

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