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Epidemiology
Original research
Long-term impact of COVID-19 pandemic on fear of COVID-19 and psychological distress among the general population in Japan: a longitudinal study
  1. Keiichiro Adachi1,
  2. Hironori Yada2,
  3. Ryo Odachi3
  1. 1 Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan
  2. 2 Department of Nursing, Yamaguchi Prefectural University, Yamaguchi, Japan
  3. 3 Department of Nursing, Shunan University, Shunan, Yamaguchi, Japan
  1. Correspondence to Dr Keiichiro Adachi; adachi13{at}yamaguchi-u.ac.jp

Abstract

Objectives The long-term impact of the COVID-19 pandemic on the mental health issues of the general population in Japan is unclear. Thus, we examined the long-term effects of the COVID-19 pandemic on fear of COVID-19 and psychological distress and determined their causal relationships among the general population in Japan.

Design and setting A longitudinal online survey was conducted by a Japanese online survey company to investigate the items regarding personal demographics, fear of COVID-19 (Japanese version of the fear of COVID-19 scale) and psychological distress (Japanese version of the Kessler 6 scale).

Participants The participants were 274 individuals (women=44.2%) with a mean age of 51.6 years (SD=13.6) who responded to the online surveys in September 2020 (Time 1: T1) and January 2023 (Time 2: T2).

Results The paired t-test showed that fear of COVID-19 decreased significantly from T1 to T2 (t=2.79, df=273, p<0.01, d=0.16). The χ2 test showed that the proportion of those at high risk for psychological distress remained the same (χ2=1.33, df=1, n.s.). Furthermore, in a two-panel cross-lagged analysis to determine the causal relationship between fear of COVID-19 and psychological distress, fear of COVID-19 at T1 significantly predicted psychological distress at T2 (β=0.26, p<0.001). Additional multiple regression analyses adjusted for covariates (age, sex, marital status, COVID-19 status, etc) showed that worsening household finances (β=0.11, p<0.05) and avoiding contact with others (β=0.20, p<0.01) were associated with fear of COVID-19 at T2.

Conclusions During the long-lasting COVID-19 pandemic, fear of COVID-19 decreased, but psychological distress did not change. In addition, fear of COVID-19 predicted psychological distress and was associated with poorer household finances and avoiding contact with others. Mental health professionals and policymakers should continue to support mental health issues following the long-lasting COVID-19 pandemic through interventions focused on promoting financial support and social interactions to reduce fear of COVID-19.

  • COVID-19
  • MENTAL HEALTH
  • Psychological Stress
  • PUBLIC HEALTH

Data availability statement

Data are available upon reasonable request.

http://creativecommons.org/licenses/by-nc/4.0/

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.

https://doi-org.ezproxy.u-pec.fr/10.1136/bmjopen-2024-084158

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    STRENGTHS AND LIMITATIONS OF THIS STUDY

    • This is the first longitudinal study exploring the long-term trend of fear of COVID-19 and mental health issues among the general population in Japan.

    • The causal relationship between fear of COVID-19 and psychological distress was examined using structural equation modelling with a cross-lagged two-panel design.

    • The study was conducted using an online survey and was limited to people with Internet who could access the survey.

    Introduction

    It has been 3 years since the novel COVID-19, which originated in Wuhan, China, in December 2019, spread worldwide. As of December 2023, the number of infected people was 770 million (approximately 6.9 million deaths) globally and approximately 4 million (nearly 74 000 deaths) in Japan.1

    In addition to the serious physical and psychological consequences of the COVID-19,2 3 isolation due to infection prevention measures (lockdown, refraining from going out, etc), economic downturn and increase in unemployment have triggered the onset or exacerbation of mental illnesses such as depression, anxiety disorders, post-traumatic stress disorder, suicide and sleep disorders.4–6 The number of people with mental health issues related to the COVID-19 pandemic also increased in Japan.7 8 For example, the number of monthly suicides increased by 16% from the previous year during the second wave of infection from July to October 2020.9

    The impact of the pandemic on the mental health issues of the general population varies depending on individual differences, including personality traits and level of fear of COVID-19.4 10 Previous studies have shown that personality traits, such as extraversion and emotional instability,10–12 and the intensity of fear of COVID-194 13–15 were associated with mental health issues such as stress reactions, anxiety and depression. In particular, a meta-analysis including 33 studies reported that fear of COVID-19 was associated with a wide range of mental health issues.16

    In September 2020, during the second wave of infection in Japan, we surveyed the general population to examine the relationship between fear of COVID-19 and mental health issues.17 In this study, we used the Japanese version of the fear of COVID-19 scale (Japanese FCV-19S)13 to evaluate the fear of COVID-19 in the participants. The Japanese FCV-19S is the first validated measure to evaluate fear of COVID-19 in Japan13–15 and has robust psychometric properties based on the item response theory.18 Consistent with previous studies, the results revealed that increased fear of COVID-19 was associated with worsening mental health.17 Over the next 2 years, the emergence of virus variants, changes in infection control measures and expansion of vaccinations led to repeated large waves of infection spread and subsequent convergence. Consequently, the economy and interpersonal exchanges gradually improved as the people continued to take appropriate infection prevention measures in the face of the strained medical situation.19 Mental health issues such as depression and anxiety peaked around mid-2020 and showed a declining trend until April 2021,20 as in other countries.21 22 However, these issues did not return to prepandemic levels.20 Although a few studies have reported a continued decline in the number of mental health problems from mid-2021 until May 2022 in other countries,23–25 to our knowledge, no studies that reported these subsequent trends have been documented in Japan. One study among medical staff examined mental health trends from February 2021 to October 2022 and reported a continued downward trend.26 However, it has been noted that medical staff and the general population differ in their risk perception, worry and knowledge about COVID-19.27 Hence, it is incorrect to discuss both on the same basis. Additionally, fear of COVID-19 among the general population in Europe decreased between April 2020 and July 2021.28 However, there have only been a few longitudinal studies of the same kind in Japan. Furthermore, the relationship between fear of COVID-19 and mental health issues has been discussed mainly through cross-sectional studies.16 Therefore, the causal relationship between fear of COVID-19 and mental health issues is unclear. Clarifying this causal relationship using longitudinal data could inform interventions targeting mental health issues during the COVID-19 pandemic.

    To address this gap, we conducted a follow-up survey (Time 2) in January 2023 among the general Japanese population who responded to our first survey (Time 1) in September 2020.17 By comparing the results, we aimed to examine the long-term trends in fear of COVID-19 and mental health issues. Simultaneously, we examined the causal relationship between fear of COVID-19 and mental health issues using two-panel data and proposed future countermeasures against mental health issues related to the long-lasting COVID-19 pandemic.

    Methods

    Participants and study procedure

    We conducted a repeated online survey across Japan. A total of 550 adults aged 18 years and older were contacted to complete the first survey (September 2020: Time 1, T1) through a Japanese online research company, Macromill (http://www.macromill.com/company/). Our previous reports used this sample.17 18 Then, we confirmed that this sample was close to the latest population estimates in Japan in terms of sex, age, gender and residential areas.18 Of the original 550 participants, 274 Japanese adults (women=44.2%) with a mean age of 51.2 years (SD=13.6) completed the second survey as well (January 2023: Time 2, T2). We excluded anyone who had difficulty reading and writing Japanese.

    The 274 participants electronically signed the consent form twice and then completed all the questionnaires. At T1, Japan was in the midst of the second wave of the pandemic; 4 months had passed since the first state of emergency had been lifted, and economic policies had been created to support individuals’ travelling and eating-out expenses.29 30 At T2, the number of infected people had increased, mainly among young people (under 30 years old), due to the spread of the Omicron variant of the virus. However, owing to vaccination efforts, symptoms had become milder and the mortality rate had improved dramatically. On 8 May 2023, about 3 months after our second survey, the Japanese government formally downgraded COVID-19 to a ‘Class 5 Infectious Disease’, the same category as common infectious diseases such as seasonal influenza, to ease COVID-19 prevention measures.19 31

    Measures

    Participant demographics

    We collected the participants’ demographics, including age, sex, residential area, marital status, number of people in the household, employment status, economic status and health status at T1 and T2.

    Psychological distress

    We used the Japanese version of the Kessler 6 scale (Japanese K6)32 at T1 and T2. This Japanese version of the original K633 comprises six items. Japanese K6 has been confirmed to have an excellent screening performance for depressive and anxiety disorders and is used in national surveys in Japan.32 34 In this study, participants were requested to rate how frequently they experienced symptoms of psychological distress during the past month on a 5-point Likert-type scale ranging from 0 (none of the time) to 4 (all the time). Total scores range from 0 to 24, and a higher score indicates more intense psychological distress.

    Fear of COVID-19

    We used the Japanese version of the Fear of COVID-19 scale (Japanese FCV-19S)13 at T1 and T2. This instrument is the validated Japanese version of the original FCV-19S4 and comprises seven items. We also examined its psychological properties using item response theory and found that it has robust psychometric properties for the Japanese general population.18 Participants were asked to rate each item on a 5-point Likert-type scale ranging from 1 (strongly disagree) to 5 (strongly agree). Total scores range from 7 to 35, and a higher score shows a stronger fear of COVID-19.

    Preventive behaviours against COVID-19 infection

    We sourced the original eight items followed by Japanese guidelines to explore preventive behaviours against COVID-19,35 including handwashing, wearing a mask, disinfecting furniture and belongings with alcohol, avoiding crowds, avoiding physical contact with others, avoiding contact with people outside the household, avoiding eating and drinking outdoors and staying at home. Exploratory factor analysis using the data of 274 participants at T2 yielded two factors (cumulative contribution ratio=69%): basic prevention and avoiding contact with others. Basic prevention included the items ‘hand washing’ and ‘wearing a mask’ (α=0.62). Avoiding contact with others included the items ‘avoiding contact with people outside the household’, ‘staying at home’, ‘avoiding eating and drinking outdoors’ and ‘avoiding physical contact with others’ (α=0.82). We used these six items to assess the extent of participants’ preventive behaviours against COVID-19 infection in the preceding 2 weeks at T2. Each item was scored on a 4-point Likert-type scale ranging from 1 (none of the time) to 4 (all the time). Total scores for each factor ranged from 4 to 8 (basic prevention) and 4 to 16 (avoid contact with others), with a higher score on each factor indicating more frequent preventive behaviours.

    Current subjective household finances compared with those before the spread of COVID-19

    We created an original item to assess the current subjective household finances of participants compared with before the spread of COVID-19 at T2: ‘How is your current household financial situation compared with before the spread of COVID-19’. Participants were asked to rate this item on a 5-point Likert-type scale ranging from 1 (gotten better) to 5 (gotten much worse). A higher score indicates a worse household financial situation.

    Statistical analyses

    First, descriptive analysis was conducted to evaluate demographic characteristics.

    Second, mean, SD, skewness and kurtosis were calculated for each psychological scale at T1 and T2. As the Japanese FCV-19S was assumed to be a normal curve (skewness and kurtosis<|2.00|),36 we conducted a paired t-test to compare the mean scores at T1 and T2. Although the skewness and kurtosis of the Japanese K6 did not meet the exclusion criteria of ≥|2.00|, the distribution was similar to the exponential distribution noted by Tomitaka and Furukawa.37 We divided participants into a risk group and normal group based on participants’ results using a cut-off score (4/5).34 Subsequently, we compared the number of risk groups at T1 and T2 using the χ2 test.

    Third, the causal relationship between fear of COVID-19 and psychological distress was examined using structural equation modelling with a cross-lagged two-panel design. The goodness-of-fit index (GFI) of the model was assessed using relative chi-square (χ2/df), GFI, comparative fit index (CFI) and root mean square error of approximation (RMSEA). A good fit was defined as χ2/df≤2, GFI>0.95, CFI>0.97 and RMSEA≤0.05, and an acceptable fit was defined as χ2/df≤3, GFI>0.90, CFI>0.95 and RMSEA≤0.08.38

    Finally, as a post hoc analysis, we conducted a multiple regression analysis (ordinary least square (OLS)), using the following independent variables based on previous studies2–6 13–17: fear of COVID-19 (T1); age, sex, marital status, living alone (yes or no), COVID-19 status (self, family and friend or acquaintance: positive or negative), chronic illness other than COVID-19 (yes or no), avoiding contact with others and current subjective household finances (T2). The dependent variable was either fear of COVID-19 (T2) or psychological distress (T2), which would be identified as an explanatory variable in a prior analysis of the causal relationship.

    Statistical analyses were performed using IBM SPSS 22 and AMOS 22.

    Results

    Demographics

    Of the 274 participants who completed the questionnaire at T1 and T2, 44.2% were women. Participants’ mean age was 48.9 (SD=13.6) years at T1 and 51.2 (SD=13.6) years at T2. The demographic characteristics of the participants are summarised in table 1. Although the mean age of the 274 participants at T1 was significantly higher than that of the original 550 participants (44.7 years (SD=14.3)), there were no differences in the mean scores of the Japanese FCV-19S at T1 (18.43 (SD=4.96) for 550 participants vs 18.06 (SD=4.88) for 274 participants) or the number of risk groups at T1 (44% for 550 participants vs 39% for 274 participants). Therefore, we concluded that our study was not influenced by sample dropout bias.

    View this table:
    Table 1

    Demographic characteristics of the study sample (n=274)

    Descriptive statistics and correlations

    Table 2 shows the means, SDs, skewness, kurtosis and Cronbach’s alphas for all the main variables. The kurtosis and skewness of all variables other than the basic prevention factor at T2 met the standard values (<|2.00|).36 Likewise, Cronbach’s alpha coefficients of all variables other than the basic prevention factor at T2 reached acceptable threshold (>0.70).39 Since the basic prevention factor showed issues with kurtosis and alpha coefficient, we excluded it from subsequent analyses.

    View this table:
    Table 2

    Descriptive statistics of main variables

    Table 3 shows Pearson’s intercorrelations between the main variables. Pearson’s correlations between psychological distress at T1 and T2, fear of COVID-19 at T1 and T2, and current household finances at T2 were significant. In addition, fear of COVID-19 at T1 and T2, avoiding contact with others at T2 and current household finances at T2 were significant.

    View this table:
    Table 3

    Intercorrelations between main variables

    Change in fear of COVID-19 and psychological distress

    As shown in table 4, the mean score of FCV-19S at T2 was significantly lower than that at T1. There was no difference between the number of participants in the risk groups for the Japanese K6 at T1 and T2.

    View this table:
    Table 4

    Differences of main variables between T1 and T2

    Causal relationship between fear of COVID-19 and psychological distress

    We examined whether demographic variables influenced fear of COVID-19 and psychological distress at T1 to confirm the covariates. The results showed that fear of COVID-19 was influenced by sex (r=−0.16, p<0.01), and psychological distress was influenced by sex (χ2=7.18, df=1, p<0.01) and age (χ2=18.97, df=3, p<0.001). After controlling for the influencing variables, we conducted the two-panel cross-lagged analysis to confirm the causal relationship between fear of COVID-19 and psychological distress. Consequently, the goodness-of-fit indices of good fit with the data were as follows: χ2/df=0.98, GFI=0.99, CFI=1.00 and RMSEA<0.01.

    The path coefficient from fear of COVID-19 at T1 to psychological distress at T2 was positively significant (β=0.26, p<0.001). However, the path coefficient from psychological distress at T1 to fear of COVID-19 at T2 was not significant (figure 1).

    Figure 1
    Figure 1

    Two-panel cross-lagged model between fear of COVID-19 and psychological distress. Age and sex are the covariates. ***p<0.001; β=standardised structural coefficient.

    Post hoc analysis

    We found that fear of COVID-19 predicted psychological distress in a prior analysis of the causal relationship. To determine the factors associated with fear of COVID-19 at T2, we conducted a multiple regression analysis (OLS), setting the dependent variable as fear of COVID-19 at T2. Independent variables were T1=fear of COVID-19 and T2=age, sex, marital status, living alone (yes or no), COVID-19 status (self, family and friend of acquaintance: positive or negative), chronic illness other than COVID-19 (yes or no), avoiding contact with others and current subjective household finances.

    The results (ΔR2=0.41) showed that a higher level of fear of COVID-19 at T1 (β=0.49, p<0.01), deteriorating household finances (β=0.11, p<0.05) and avoiding contact with others (β=0.20, p<0.01) were correlated with a higher level of fear of COVID-19 at T2.

    Discussion

    This study aimed to clarify the long-term trends in fear of COVID-19 and pandemic-related psychological distress and the causal relationship between these through two surveys (T1: September 2020; T2: January 2023). The results showed that fear of COVID-19 decreased significantly from T1 to T2. However, no significant difference was found regarding psychological distress between T1 and T2, and approximately 30% of the participants still belonged to risk groups (the Japanese K6 score≥5) at T2. Our examination of the causal relationship between fear of COVID-19 and psychological distress using two-panel cross-lagged model data revealed that fear of COVID-19 significantly predicted psychological distress.

    Regarding the psychometric properties of the main variables, the basic prevention factor showed issues with kurtosis and alpha coefficient. When we checked the distribution of this factor, 61% of the participants scored 8/8 and 20% scored 7/8. Previous research reported that many people in Japan continued wearing masks following the Japanese government’s request, even after vaccination.40 This tendency caused the ceiling effect for the basic prevention factor.

    Consistent with Mertens et al,28 who found that fear of COVID-19 gradually decreased from April 2020 to June 2021, our results showed that fear of COVID-19 decreased from T1 to T2. At T1, the state of emergency had been lifted, and Japan resumed economic activities with recovery measures after the peak of the second wave. During this time, people were urged to participate in economic activities while following strict infection prevention measures.29 30 While the number of infected people at T2 increased, vaccination efforts led to milder symptoms and a drastically lower mortality rate.19 At this time, the Japanese government eased COVID-19 prevention policies and also announced that, a few months later, COVID-19 would be given the same classification as that given to seasonal influenza, that is, ‘Class 5 Infectious Disease’.19 31 These factors likely led to a lower fear of COVID-19 at T2 than that at T1. However, no change was observed in psychological distress between the two-time points. At T2, the proportion of people at risk for psychological distress (K6 score≥5)34 was more than 30%. Moreover, the proportion of people with serious psychological distress (K6 score≥13)32 41 was 7%, which was approximately double the pre-COVID-19 pandemic rate (3.6%).38 Previous research reported that the proportion of the general population with mental health issues such as depression and anxiety peaked in mid-2020 and gradually decreased through 2021 but did not reach prepandemic levels.20 Although mental health problems among healthcare workers decreased from February 2021 to October 2022,26 the impact of the COVID-19 pandemic on the social life of the general population has not fully dissipated 2 years later.19 Our results suggest that the COVID-19 pandemic continues to impact mental health issues in the general population.

    In this study, structural equation modelling using a two-panel cross-lagged analysis confirmed a causal relationship in which fear of COVID-19 significantly predicted psychological distress. To date, many studies have noted the relationship between fear of COVID-19 and various mental health issues.16 However, these studies used cross-sectional data, and the causal relationship has not been determined. In this sense, this study is, to our knowledge, the first to report the causal relationship between fear of COVID-19 and mental health issues in not only Japan but also other countries. Additionally, as shown in the post hoc analysis results, the factors significantly associated with fear of COVID-19 at T2 were current household finances and direct interactions between people. With the resumption of people-to-people exchanges centred on economic activity support currently underway in Japan, fear of COVID-19 is expected to continue to decline, leading to a corresponding decline in mental health issues.

    In other countries, such as Japan, the number of mental health problems during the COVID-19 pandemic increased two to three times compared with before the pandemic42; these numbers decreased from mid-2020 to mid-2022.21 23 However, they did not return to prepandemic levels,22 as found in the current study. This is partly due to the COVID-19 public health and social measures (PHSM) implemented in each country, such as lockdowns, mask-wearing, restrictions on social interactions, border closures and vaccinations, depending on the infection situation43 44; Japan is no exception. In this sense, this study’s findings may contribute to reducing mental health problems related to long-lasting COVID-19 in other countries.

    Study limitations

    First, participants were recruited online for this survey. There was a close relationship between mental health issues and economic conditions during the COVID-19 pandemic.7 As it is difficult for people in economically disadvantaged situations to participate in and respond to online surveys,45 it is likely that this study’s participants are not representative of the general population in Japan. Second, this longitudinal study had a long interval of approximately two and a half years. This study’s findings were based on a comparison of two-time points, which were two and a half years apart, and the data were not collected regularly during the pandemic. As mentioned above, in the past two and a half years, Japan experienced multiple waves of the pandemic, rolled out vaccinations, experienced various COVID-19 variants and underwent changes in infection prevention measures. We could not assess detailed changes in the fear of COVID-19 and mental health issues related to various phases and for the accompanied events associated with the long-lasting COVID-19 pandemic. Finally, this study used a cross-lagged effects model to infer the causal relationship between the fear of COVID-19 and psychological distress. However, several points regarding causal inference using the cross-lagged effects model have been pointed out.46 47 In particular, confounding factors that do not change over time (time-invariant confounding factors), such as innate temperament and constitution, may distort the assessment of causal relationships.47 In this analysis, age and gender were incorporated into the model as such time-invariant confounding factors, but other unknown confounding factors have not been sufficiently searched for. Therefore, the causal relationship found in this study may not be conclusive.

    Future avenues for research

    This study examined a causal relationship between fear of COVID-19 and psychological distress. However, this point requires further consideration. In the future, further time-invariant confounding factors must be considered, and analyses with other extended cross-lagged models are needed.46 In addition, psychological distress did not significantly change from T1 to T2. These findings are based on two online surveys conducted two and a half years apart. We should monitor future developments regularly in terms of psychological distress, the COVID-19 pandemic and the people-to-people exchanges centred on economic activity. Furthermore, to clarify the long-term effects of the COVID-19 pandemic on mental health issues, further follow-ups are necessary while considering other survey methods.

    Conclusions

    This is the first long-term longitudinal study to investigate the causal relationship between fear of COVID-19 and mental health issues. The results showed a causal relationship in which fear of COVID-19 significantly predicted psychological distress. While fear of COVID-19 decreased from September 2020 to January 2023, there was no change in psychological distress, which remained higher than before the COVID-19 pandemic. When thinking about how to deal with mental health issues during the COVID-19 pandemic, considering fear of COVID-19 could be helpful. In particular, interventions designed to provide financial support and increase opportunities for interpersonal contact would be effective to reduce the fear of COVID-19 among individuals.

    Data availability statement

    Data are available upon reasonable request.

    Ethics statements

    Patient consent for publication

    Ethics approval

    This study involves human participants and was approved by The Ethical Review Board of Health Sciences, Yamaguchi University Graduate School of Medicine (Number 737-1). Participants gave informed consent to participate in the study before taking part.

    Acknowledgments

    The authors would like to thank Editage (www.editage.jp) for manuscript review and editing support.

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    Footnotes

    • Contributors KA, HY and RO designed the study, obtained funding and were involved in data analysis and interpretation. KA wrote the first draft. KA, HY and RO critically reviewed and revised the drafts and approved the final manuscript. KA accepts all responsibility for the work and the conduct of the study, has access to all the data and controls the decision to publish. KA is the guarantor.

    • Funding This work was supported by the research project ‘The COVID-19 Pandemic and Time Studies’ of Yamaguchi University Research Institute for Time Studies.

    • Competing interests None declared.

    • Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.

    • Provenance and peer review Not commissioned; externally peer reviewed.