Background

Coronavirus disease 2019 (COVID-2019) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an ongoing global pandemic. The clinical outcome of COVID-19 ranges from mild respiratory failure to severe disease with high risk of fatality [1]. As of July 26, 2021, the global COVID-19 dashboard shows 194,723,719 coronavirus case patients, 4,167,618 deaths [2]. Recent studies have reported that at least the one in four COVID-19 recoverees suffer long-term impairments such as fatigue and taste/smell disorders [3].

A decrease in the ability of the lungs to diffuse carbon monoxide was often found in patients who recovered from COVID-19 [4], suggesting that respiratory dysfunction may remain after recovery [5]. A recent study by Ballan and colleagues followed up patients three to four months after COVID-19 recovery and reported the following long-term physical impairment: 13 (5.5%) Dyspnea, 12 (5.0%) ageusia, 11 (4.6%) anosmia, 14 (5.9%) arthralgia, 14 (5.9%) myalgia, and 53 (22.3%) limited mobility and 113 (51.6%) decreased vital capacity[6]. Those conditions after COVID-19 have been named as post-COVID conditions. “Experts around the world are working to learn more about short- and long-term health effects associated with COVID-19, who gets them, and why (Centers for Disease Control and Prevention, 2021)” [7].

Mental health problems, as well as physical disabilities, have been observed in people post their recovery from COVID-19. In terms of mental health problems, symptoms of post-traumatic stress disorder (PTSD), depression, or anxiety have been observed in people who recovered from COVID-19 [6, 3).

Table 3 The results of the logistic regression model
Full size table

Discussion

The principal findings

The objective of the present study was to identify post-COVID conditions and investigate the relationship between post-COVID conditions and mental health status. We conducted an online survey in two countries and collected valid responses from a total of 763 participants, including 135 with a history of COVID-19. Of the 135 COVID-19 infected participants, 37.0% (n = 50/135) had some post-COVID conditions. The major post-COVID conditions reported were fatigue/tiredness (n = 19/50, 38.0%), dysgeusia (n = 13/50, 26.0%), olfactory dysfunction (n = 12/50, 24.0%). The COVID-19-infected respondents showed greater incidence of all mental health symptoms investigated in this study, including symptoms of COVID-19-related anxiety, depression, generalized anxiety, and post-traumatic stress. Greater impairment of mental health was observed in the participants who had developed COVID-19 with post-COVID conditions than those without one. Furthermore, our results suggest that mental health was impaired in the presence of post-COVID conditions.

The implications of the findings

The group that developed COVID-19 has worse mental health than the group not infected with SARS-CoV-2. In the group with COVID-19 experience, 43.0% (n = 58/135) people reported having some sort of mental disorder. In addition, in the COVID-19 experience group, the percentage of people who exceeded the cutoff was 39.3% (n = 53/135) for depression, 24.4% (n = 33/135) for generalized anxiety, and 50.4% (n= 68/135) for PTSD. The participants infected SARS-CoV-2 had significant psychiatric symptoms compared to the participants had not be infected. The results are consistent with those of (i) a cohort study of inpatients with COVID-19 for a one-month period in Helsinki [37], (ii) a British community cohort study [38], and (iii) an American electronic health record network cohort study [39]. The latest systematic review shows that the incidence of depressive symptoms is 10.0–68.5%, that of clinically significant anxiety is 5.0–55.2%, acute and post-traumatic stress is 7.0–36.4%, and fatigue is 12.7–88.6% [40]. The evidence indicates that SARS-CoV-2 infection may increase the risk of develo** mental disorders such as depression, anxiety disorders, and PTSD [39].

The incidence of long-term COVID-19 health hazards was 37.0% (n = 50/135 after COVID-19 among Japanese and Swedish participants in the present study; relatively common post-COVID conditions were fatigue/tiredness (n = 19/50, 38.0%), dysgeusia (n = 13/50, 26.0%), olfactory dysfunction (n = 12/50, 24.0%). The other frequently observed post-COVID conditions in our study is cough (n= 8/50, 16.0%). These results are consistent with previous studies in which most patients had abnormal respiratory function at 3 months [41], meaning that patients with acute symptoms of COVID-19 that were severe enough to require occasional ventilation may have impaired long-term respiratory function. Fatigue/tiredness was reported at 38.0% (n= 19/50) in infected respondents in this study. Fatigue after COVID-19 may be associated with lung, cardiovascular, liver, kidney, cognitive, and neural function in some SARS-CoV-2 infected individuals experiencing serious complications during the acute phase [42,43,44,45,46].

Furthermore, the logistic regression analysis showed that the participants with post-COVID conditions were at a higher risk of develo** mental disorders than those without one. Historically, non-major symptoms of infectious diseases have been neglected; a COVID-19 long-hauler reported that his medical doctor/practitioners disbelieved his physiological distress [47]. The results from our study can provide practitioners and clinicians with evidence of late-onset long-term symptoms in SARS-CoV-2 infected individuals and suggestions for the risk of subsequent development of mental disorders. The findings also contain information that will help medical policymakers make decisions, highlighting the need to provide long-term medical-psychosocial support services to patients infected by SARS-CoV-2.

Of the participants who had not developed COVID-19, 30.3% exceeded the PHQ-9 cutoff. This result suggests increasing risk of develo** clinically depression in the citizens as a whole during pandemic. Our finding is similar to the results of the latest meta-analysis that reported that the prevalence of depression during the COVID-19 pandemic was 25% (ranging from 7.45% to 48.3%) [48]. Therefore, although caution is required in the interpretation due to the non-random sampling procedure, our results indicate that clinically significant depressive symptoms in the general population in Japan and Sweden might be common during the COVID-19 pandemic. In the United States, Ettman et al. (2020) reported that the prevalence of clinical significantly depressive symptoms (the total PHQ-9 score ≥ 10) in the general population increased from 8.5% to 27.8% during the COVID-19 pandemic [49]. Without public health crises such as the COVID-19 pandemic, the ratio of PHQ-9 scores above this threshold for the general adult population has been approximately 6%: 6.5% in South Korea, 5.7% in Japan, and 6.4% in 27 European countries [50]. A recent meta-analysis also suggested a one-year prevalence of depression of 7.2% in 30 countries around the world [51]. The results of the study and the global prevalence of depression demonstrate that people's mental health is compromised during a pandemic, even without lockdown, as seen in Japan and Sweden. Limitations of interpersonal interaction, leisure, and other activities owing to the COVID-19 pandemic, may be associated with exacerbation of depressive symptoms [52, 53].

The results of this study suggest that many COVID-19 survivors have a long-term psychical impairment. A cohort study in Sweden reported that one out of five inpatients required rehabilitation intervention even five months after discharge [54]. These findings indicate that the next direction should be building a system that provides rehabilitation interventions to an unprecedented number of people suffering physical impairments, such as post-COVID conditions. Furthermore, our results show that people's mental health deteriorates with or without a COVID-19 experience during the pandemic. Therefore, the decision-maker should introduce or recommend an intervention format for people with support needs due to mental health problems. Cognitive-behavioral therapy (CBT) may be a promising approach even during the COVID-19 pandemic. Cognitive-behavioral therapy is a highly effective psychotherapy for major depressive disorder, anxiety disorders, and PTSD [55, 56]. Internet-Based CBT (ICBT) via videoconference or web-based program also is as effective as face-to-face CBT [57,58,59]. Remote treatment such as ICBT does not require people to visit the hospital and may help reduce the risk of SARS-CoV-2 infection. ICBT is also a cost-effective treatment approach that optimizes relatively few therapist resources [60]. ICBT is employed widely in Sweden [61], but not in Japan [62]. In addition, some recent clinical trials have suggested that ICBT is feasible and effective for anxiety disorders in Japan [63, 64]. Therefore, Japan should accelerate efforts to introduce and implement this intervention as broadly as Sweden.

Strengths, limitations, and directions for future research

The present research has four strengths. First, our results suggest that post-COVID conditions represent a risk for mental illness, and they have deepened our knowledge of the relationship between post-COVID conditions and mental disorders. Second, participants in the present study also included data on patients with relatively mild COVID-19 who have not been hospitalized. Thus, the findings of this study may be applicable to patients with differing severities of COVID-19. Third, the present study population was diverse because this study was conducted in two geographical regions, Eastern Asia and Northern Europe (Table 1). The fourth strength is that the participants have not been intentionally exposed and treated by a particular medical facility because the present research was an online study of cross-sectional study design (Wang and Cheng, 2020) [65].

The limitations of the present study include the nature of the sample, the test format, and accessibility. First, in the survey most respondents were adults in their 20 s and 30 s in the Swedish data set. In contrast, there were few respondents aged 50 years or older. Elderly people, who often have chronic physical illnesses, are a group that demonstrate more serious symptoms of COVID-19 [66, 67], which can be more detrimental to post-COVID conditions and mental health [68]. In future studies, conducting research with a larger sample size and analyzing them by age group is necessary. Second, all mental health measures were rated on a self-rating scale. Although the data collected was well-validated and the severity of clinical symptoms was credible, clinical symptoms alone do not confirm any mental disorders. In the future, cross-sectional populations should be assessed using telephone interview and using diagnostic classification tests conducted in semi-structured interviews by trained clinicians. The third limitation was that the population may have belonged to a relatively wealthy social class with a high degree of education, information and communication technology (ICT) literacy, and possession of an internet environment and devices. Populations who have access to the current online research will probably have more opportunities to learn about co** strategies and receive medical services for post-COVID conditions, as they will also have access to appropriate medical information via the internet. The prognosis of COVID-19 may be worse than the results of this study when a population sample with low ICT literacy and low education level is included. That is, the results of this study may have provided more optimistic data. For future research, it is recommended to include community samples through face-to-face assessment. The final limitation was that we did not investigate the length of time suffering from physical symptoms. Due to this limitation, our results do not clarify the effects of the duration of physical symptoms on mental health.

Conclusions

The result of our research suggests that post-COVID conditions occur in about 40%. The SARS-CoV-2 infection may cause long- and short-term health hazards and increase the risk of mental disorders. Therefore, medical policy regarding COVID-19 should include long-term clinical practice to address long-term symptoms and mental health risks.